The first generation of Pokemon is the simplest one in many aspects of it's mechanics, and it suffers from certain hiccups in design that were pretty common in old RPGs, stuff like certain glitches in the Pokemon's movements, having to go from point A to point B just to get an item to go back and access another area form point A, certain maps (caves) being a bit frustrating the first time and so on.

Still, the first generation has something in these hiccups, most glitches actually won't pop up unless you search for them, and those hunts for items or not knowing where to go are pretty much absent in current Pokemon games, and although I know the HMs are not very popular, having to distribute certain Pokemon to use them added if only just a little bit of strategy to what is a very simple and, let's be honest this is a kids game, easy game.

The overall vibe is also different, these being the first steps in a franchise that nobody could've predicted whould become so big, certain bits of the lore, the Pokemon, the people and the world in general feel a bit different or even off, it gives the impression at times that Pokemon were supposed to be treated more like domesticated monsters rather that this world's equivalent of animals that we get now.

If someone wants to play gen 1, I'd recommend the GBA remakes honestly, they are a step up in every way, but these games with falws and all were a fenomenon of their time for a reason, and they have a charm unique to them.

This is not my favorite gen by far, but is one that is fun to revisit once in a while.