Look at real life, now the game, now back to real life.
Notice how there are hundreds of thousands of different kinds of nearly the same thing. A simple thing like "fish", has millions of different species, yet Pokemon only have around 10? Seems like there aren't nearly enough Pokemon with similar features. For a world like Pokemon to be realistic, saying something like "we already have a bat pokemon, zubat" is ridiculous.
The world thrives on variety, its not just a collectible game, but also a world where "fish" don't exist, only Pokemon. I have problem at all, and honestly wish they would add more Pokemon of similar species.
I consider this gen to be a new beginning. It's been quoted over and over, but not having any of the old Pokemon in the new world makes it feel so much newer, even if the basic building blocks are the same. It's like getting a new Lego set, sure its still Legos, but now you have different shapes, colors, and other niche effects to play with. It's also the first Pokemon game I could convince an otherwise anti-Pokemon person to try out, and eventually enjoy. The game has been streamlined, no longer requiring you use HM's all the time for everything, which allows for a much greater freedom in team creation during the game.
You could consider it a restart, but I feel like to have a "pure new beginning" would mean no longer doing a turn based game, or no longer having a 6 party limit, or other huge over-arching changes. Which will never happen because far far to many people enjoy the mechanics as they are now. So this is the closest you're ever going to get to a "new beginning".
