The thing is Pep Barca changed many things universally in the game. What Busi used to stand out doing in the past in 2011, are now things that are present in most top DMs. He ain't that innovative right now.
Elements from that team have been adopted by most managers so now we find them in many teams. Does DM that drops often to pick up the ball is that uncommon now? Nope. Chelsea of all teams has one. Are keepers who are good with the ball a novelty these days? Hell no, now a keeper that is shit with his feet stands out even more than a guy who knows how to pass. Is False 9 surprising to see these days? Not at all, several teams play with a version of that.
Busi might've been unique in 2011, now the only thing that stands out about him in a clear way is how slow and weak he is defensively without the ball.
Are we talking about 2021 Busquets? or prime Busquets? If it is the former I agree but if it is the later it is insulting to one of the smartest players in the history of the game.
Busquets wasn't just a guy who connected defense with midfield, he was elite all around DM who had it all, his defense was always on point, always at the right place at the right time, always making the right play, always able to provoke opponents, invite pressure without giving the ball.
But father time is undefeated as Sir Charles Barkley always say and it hit Busquets early, at first he wasn't able to cope with counter attacks, then he wasn't able to be at the right place at the right time because his legs isn't quick enough for the decisions his brain take, now even his own ball skills are suspect and usually needs a rest in order to be able to show it.
But even in 2021, his ability to connect defense with midfield for a sole DM isn't as common as you make it, not that many top DM can do it and mostly they are more comfortable in 2 DM system where the load is shared on 2 players.
Make no mistake, replacing Busquets is a must but the process will be more painful as you think.
I don't blame our coaches for having him as a starter tbh, our alternatives are meh at best. We need to prioterize a starting DM in the market