1e literally had examples on how to blend the game with other games such as Boot Hill, Gamma World, etc.

We played all three but never combined them.

They have guns and smoke powder in 5e and it just doesn't feel right.

Game of Thrones with cowboys carrying torc grenades?

I feel like as the game evolved to fit more of a trope-y Tolkienesque quasi-medieval setting it definitely got more and more out of place. 1e, especially earlier on, and before was much more of a genre mishmash. Fantasy in the truest sense.

We never combined them either but I did find it cool that the 1e DMG gave explicit advice on how to do so. Heck, there was even that one module where the characters can find laser weapons. [1]

[1] https://en.wikipedia.org/wiki/Expedition_to_the_Barrier_Peak...

> They have guns and smoke powder in 5e and it just doesn't feel right.

One of the settings for the game that became OD&D included far-future alien technology (Blackmoor), so there's long been precedent.

I never played 1e, I started with ADnD 2e.

Yeah, things started shifting with 2e and that shift kept going further and further.

With Forgotten Realms it shifted from more of a pulp swords & sorcery to a medieval-ish Tolkien-esque environment.

Over time it shifted from low fantasy to high fantasy.

And not only did the theming start to solidify, but over time the tropes arguably became self-reinforcing.

Every campaign I can remember from that era was customized enough that the players and DM would joke about it being "2.5e".