How to Convert 5e Players: The World Within a World Strategy

I'm going to lead with this: if someone is happy with 5e, they're going to stay with 5e. But, maybe, possibly, you can get them to TRY another game, and maybe they can learn to appreciate another game! I have had an epiphany!

I can't be the only person who has ever had the idea "what if our D&D characters made their own D&D characters and played D&D? How meta!"

The premise: You give the players characters (not the players) a situation in your game where they can play another TTRPG for a reward. A reward is better than avoiding a consequence, but you can layer both. Maybe a traveling magical stranger come along and offers the PCs a chance to play a magical game for fabulous prizes. Maybe they meet a mad wizard who got trapped in a secondary world, that is to say, a world within a world like the Matrix or some Isekai. That secondary world has different rules. To go into that world, the characters will have to play by those rules - like the Savage Worlds, Shadowrun, Shadowdark, or GURPS or whatever. I'm sure you can make up a situation that suits your own game.

Tips:

Use incentives! If their 5e D&D characters can complete the 1e D&D adventure you have prepared for them, their 5e characters can magically keep a magic item their 1e characters earned. Offer them something NICE like a +3 item.

Make sure it's a choice! Don't force it on them. But you could.

Split the party. Its magical wibbly-wobbly timey-whimey BS and it doesn't interfere with normal passage of time. Don't let a pesky thing like democracy stop willing players. Run a side-game for them. Work around the party-poopers so they don't feel spurred.

Make the medicine sweeter! Don't just give them a loser 1e D&D character sheet, give them a really impressed 1e D&D character sheet. Unless they'd be into a character funnel.

Justification: Maybe the players need a palate cleanser; Do this instead of a one-shot. Maybe they've just finished an adventure and you don't have the next adventure prepped yet. This is your excuse for delaying.

Have respect for their time: Structure this like a one-shot! Try to keep it to a one-session thing.

Leave them wanting more: At the end of the PCs brief stint into the secondary world, when everything feels wrapped up, you're going to give them another adventure hook! Like a treasure map to a ruin with a ton of treasure, or their own star ship.

Make it Easy: Hand out pre-generated characters. Don't spend game time making characters. Leave out some of the more complex options.

You're Doing Tieflings Wrong

Tieflings do not have a standard skin tone, and 3e did not assign them standard physical features.

Look up Tieflings online in the D&D 3.5e SRD. "Many tieflings are indistinguishable from humans. Others have small horns, pointed teeth, red eyes, a whiff of brimstone about them, or even cloven feet. No two tieflings are the same." Note the use of the word or in the list of physical features, not and. And definitely note that the description reads "many tieflings are indistinguishable from humans". This is the full physical description and does not address skin color. This passage comes from the monster manual (where tieflings used to be) and the physical book provides an illustration of a woman who looks like an ordinary human.

For reference, even the description of tieflings in 2014 5e PHB, under the subheading "Infernal Bloodline" reads "Their skin tones cover the full range of human coloration, but also include shades of red." The red skin thing is new in 5e (or maybe it was 4e?) and it suits cambian demons, which are creatures with a human parent and an infernal parent like Hellboy.

In 3.5e, Tieflings are categorized with Aasimar under Planetouched in the Monster Manual. Quote: "Planetouched is a general word to describe someone who can trace his or her bloodline back to an outsider, usually a fiend or celestial." To reiterate, if you're a tiefling, you have a fiendish ancestor. That's bad. Here's why. Tiefling alignment is given as "usually evil (any)". The alignment of usually evil is the basis for discrimination against tiefliings. To quote 3e's definition of evil: ""Evil" implies hurting, oppressing, and killing others. Some evil creatures simply have no compassion for others and kill without qualms if doing so is convenient. Others actively pursue evil, killing for sport or out of duty to some evil deity or master." THIS is this the bases for discrimination against tieflings. Evil alignment in 3e is traditional black-and-white-morality, objectively bad.

Story Structure in TTRPGs

TL;DR, never call Act I an introduction. That's massively underexplaining what Act I is. Also, I worked out a really good reason not to play 5e D&D.

In story structure, Act I is the set up, Act II is the execution, and Act III is the resolution. 

In Act I, you set up the story. By the end of Act I, the themes, major characters, setting, conflict, stakes, and the goal should be established for the audience (or participants in TTRPGs). Act I ends when an event or action forces the hero (or by choice of the hero, but usually it's not their choice) to put their normal life on hold to engage with that conflict and pursue that goal. The number of choices available to the hero are greatest in Act I.

Act II is where you execute that story set up in Act I. If you set up a mystery, you execute the mystery, etc.  Act II is the longest act. Act II is about the hero engaging with escalating obstacles and risks in the setting as he pursues his goal. Obstacles (AKA trials) prepare the hero for their goal, first by testing the hero's skills and revealing his weaknesses or flaws, then by taking away his resources or nullifying his strengths, and by giving him lessons that make him stronger or wiser. Obstacles force heroes to confront failure; they force heroes to change or grow. Throughout Act II, minor characters and subplots may be expanded on or introduced, and are resolved before the end of Act II. During Act II, the hero's choices are narrowed down. By the end, the hero commits to one path. Act II ends when the tested and tried hero has overcome the obstacles and has learned from them, and is finally ready to confront the main antagonist.

Act III is where you resolve the story set up in Act I. It begins with a final confrontation with the primary antagonist that shows the hero's growth and how that growth made them worthy of their goal. Act III ends showing the audience the consequences of the hero's choices on the world; the world is not reset.

In good TTRPGs, Act I looks a bit like this: You ask the players what they want, give them some opportunities to get it, establish the obstacles that each choice will force on them, let them choose their preferred opportunity, then set them loose. I might even suggest working this into the ending of the previous adventure so that you start the next adventure with momentum. In D&D 5e, you pick one pre-written campaign book with a preset path and story.

In TTRPGS, Act II depends on the game you're playing. In 5e, you smash things, level up, gain powers, smash bigger things, level and gain more powers, and smash bigger things. Repeat until the second biggest thing is smashed and the players get some McGuffin. All while following a story that's already been written and is intended for general audiences.

In TTRPGs, 5e specifically, Act III is an obligatory fight with a damage sponge and a whole lot of cheap powers. Then you win the D&D. Seriously, why are you playing 5e? Stories are fundamentally about showing a character growing from a state of immaturity to maturity and imparting a lesson (a theme). Ever wonder why they call the moral of the story a theme? Stories are satisfying when a need for the growth is established in Act I, when the growth is earned through struggle in Act II, and when Act III reveals the results of that growth in a way that reinforces the lesson of the story. This character growth themes the story.