Nomura is valuable. He was smart enough to negotiate some sort of contract that meant his name appeared even on art renders and the title screens of games as a credit, and he and his art style have become synonymous with Final Fantasy and Square Enix. Don't just take it from me - Yoshinori Kitase himself said as much:
"Nomura's [art] direction is perfect. That's the kind of visual concept that Final Fantasy should stay with."
What I'm saying is that no matter how badly he fucked up, Square Enix would - and likely did - all they can do in order to hold on to him. He's a figurehead. An important name. An important style, to them. So they've kept him. It's pretty plain that he walked from FF15 before he was forcibly pushed, though, and it's seeming fairly likely from some of the comments made by Tai Yasue in interviews he did around KH2.5's release that
he is in charge of KH3 overall, not Nomura. But Nomura is worth keeping around; he can piddle around and contribute art to a variety of projects, but I think it's pretty likely that most of his actual directorial power has been stripped from him as a response to his failures. They'd never fire him, though. That'd be too much of a loss.
It's not like this sort of sidelining would be new for Square anyway - this is what happened to Sakaguchi post-TSW, with them sapping duties and power from him left and right but keeping him around for a few years as a figurehead. They'd trot him on stage at the occasional show, but for that last stretch at Square Sakaguchi wasn't doing nearly as much, the price of his failure. The difference with Sakaguchi was that he was a maverick and a rebel at least by Japanese standards - it's how he found his success (see also: Kojima), and after a bit of time on the leash in that manner he said 'yknow what, fuck it' and left and did his own thing. Nomura is I believe a bit of a diva - as people so hugely talented often are - but doesn't have that streak either. I think he likes Square (despite his 'burning anger' mentioned in the Famitsu interview after leaving/being kicked from FF15) and likes the comfort.
I think his days of directing alone are over, though. Done. I don't think Versus' long development time was entirely down to him - there were other contributing factors including Crystal Tools being a fucking mess and people from all SE Japan teams - including that team - being parachuted into the failures of FF13 and FF14 development to finish & fix them respectively, but it's clear from the meandering development we saw and the lack of focus in what we saw over the years that there were issues with the vision for the game. The buck for that stops with him, and he paid for it in the end.