>>43511819A LOT of development time went into it.
They discarded pretty much everything they had at one point in order to fix everything they did wrong and make it better. We know they completely redid the sprites at least twice, they even redesigned nearly all Pokémon at one point.
This is often a necessary step in software development, but not one you can take often, as bean counters don't understand why starting over would significantly improve the final result, nor why that would be preferable to a rushed out, semi-finished product.
Now, the Pokémon Company decides when the games are to be released and guess what: they want new games ASAP, so they can sell merch. So there is no time for polish. The current gen didn't even have time for polish even though they cut out half of all Pokémon to save on work.
If you want good games again, give Game Freak enough time.
And hire a new writer, preferably one of the old Genius Sonority ones, good lord, this series needs things to be different and a story that can stand on its own legs, with villains whose plans make sense and who don't abide by the rules, meaningful player choices (proptip: "Will you help me? -> No -> Too bad, this will Loop until you press yes -> yes -> WOW, THANKS A LOT" is not a choice).
