Since it would seem my previous statement didn't convey what I was trying to say, I have conducted an analysis of how represented Gen I pokémon are when it comes to play mechanics. I am only taking account aspects of battling and collecting. I am not counting instances of an NPC referencing another region/generation or the appearance of NPCs from different games. To me these are very low impact overall and are clearly just there for story building. When it comes to pokémon, the core is... well... the pokémon themselves. I have scored each Gen using the following metrics:
Mega Representation: How many pokémon from that generation can Mega Evolve.
Regional Variants: How many pokémon from each generation with a known regional variant.
Exclusive Z-Crystal Representation: How many pokémon from that generation can use an exclusive Z-Move. For this study, Alolan Raichu is counted as Gen I since it is an regional variant of a Gen I pokémon.
New Babies Added After Introduction: How many baby pokémon were added to older lines each generation.
New Evolutions Added After Introduction: How many new evolutions were added to older lines each generation.
Starter Recycling per Gen: How often pokémon from a given generation were used as starters per generation. Paired games (ex: FRLG) and core games with a follow-up (RuSaE) are only counted once. I am not counting non-core games like Pokémon Mystery Dungeon.
From my research, Gen I typically gets at least a good representation in each gen's newer mechanics, occasionally even moreso than the gen's own pokémon (specifically megas in gen 6). This is what leads to fatigue with "Kanto" and Gen I. This isn't even counting the sheer number of times we have stepped into the region, which is 4 out of 7 gens. Couple that with how much outside marketing (TCG, anime, etc) ties directly to Gen I pokémon and it is easy to see why people are ready to see some of the other pokémon take the spotlight for longer than just for their individual generation.
I also want to follow, as I feel I will have to defend this stance, that I am not saying I hate Gen I. I really like it. That being said, I also like other gens and would like them to begin to be more equally represented when new additions are made.