Correct, but this isn't a consequence of Guardiola "coaching things out of his game". It's a consequence of City itself not giving him the context to be more of a maverick. At Villa he had to try and make things happen in the final third, against back-pedaling defences and with teammates making runs with abandon - because that was 80% of their attack. At City he plays with guys who are much better than him at making things happen in the final third, has fewer opportunities to carry the ball in transition, and often when he does he doesn't have multiple teammates making runs, instead the team wants to stop and set up their attack in other team's half. That's why he looks boring and mechanical
Because he evidently wasn't good enough to deserve it. City have De Bruyne
Oh, and it's not true that he doesn't try and take people on. He tries that all the time. He's just not a good enough dribbler to consistently beat his man quickly in the kind of spaces he operates in now - lacks the acceleration and/or agility for it - and as a result often ends up drawing a second defender to him, at which point he makes the right play: a 10 yard lay off for a teammate, the one that's now been left wide open because his defender is helping on Grealish. In the few instances in which he has the space and the time attack a defender 1vs1, he often beats him(unless the defender backs away so much he doesn't need to)
You can't use the first sentence as a run-on and not see the contradiction, surely? Every human on the planet gets better by doing, repetitively and expediently until they are determined masters of a skill/craft. By removing the opportunities to even explore that element of his game, Grealish is reduced - or marginalised - as a specialist with a specific job to do in the team, one he's the best in the entire league at, and very probably the reason he was targeted by City in the first place, but a specific job nonetheless.
Your posts highlight it - get from point A to point B and then pass it to someone better than you are at the next phase. This can be considered optimisation, because, in a way, it is. But it can also be considered marginalisation because there's a glass ceiling to what Grealish is allowed to do and what is frowned upon because his attempt from that point onward can be taken on by - in your own words - someone better than him in the next third of the pitch.
This can be seen as a matter of perspective - is Grealish better or worse for being optimised? By removing all form of expression, but having him run like a battery at what he is exceptional at, is he a better or worse player? An underutilised one, or not? If we were using American Football terminology, Grealish is/was a sure thing as a yard gainer, which is an invaluable asset for any team, not just Guardiola's. Having a player that 9/10 times can gain you 30+ yards is a cheat code in itself for the sheer consistency of it. In the minds of those who went out and got what Guardiola asked for (some form of yard gainer, I'm sure), City were provided with an asset that really allowed and afforded them to play in a different way, that, in part, was less team-based, as Grealish could gain those umpteen yards by himself, instead of by how City used to progress those same yards as a unit, which takes time, effort and a lot more pieces optimally in place to accomplish.
Guardiola has said himself that ball carriers and dribblers are the cheat code for what they enable a team to do in a fraction of the time, and in his world, it makes perfect sense to have used Grealish as he did, with him passing the baton off when he got to the - for him - hard yards. At other clubs, under managers who don't see the game in such a binary fashion, the "Villa Grealish" goes on to a bigger club and isn't anywhere near as efficient as Guardiola made him, but becomes a better version of the player he got to that club as. Better decision making; better understanding of the game; better understanding of self and when and what to do in certain positions/situations via the aforementioned honed and refined practice, etc. etc.
As I've said to you before, Grealish is the other side of the coin of system cog verses expression; he and Foden, both, on opposite ends of the spectrum, which makes them perfect case studies. One cannot determine whether the Grealish we got to see is better/worse than the one who made his name. We can say that Guardiola brought him success and made him an important and essential cog. But it can be said with utmost certainty that Guardiola made him boring, predictable and perfunctory - do what you're good at, and don't dare overstep your mark. It's the very definition of expressionism lost, even if we understand why and the [clear & vital] benefit of it.
Through the eyes of a fan of flamboyance and expression, Guardiola getting his hands on this type of player - one he deems exceptional for one thing, but not good enough for the other - it's got to be seen as a loss "to the game" because one stem of free-flowing expressionism has been lost, and another Grealish then has to take on the mantle because the one that was there no longer has his. The problem here is, Grealish's don't come around often, which is why it's going to be seen as sad when one is lost to the system despite the success it brought the club who purchased him.