The problem with trying to fit all these things into one or a few different stats is that it's really, really hard to quantify most of these things. Or to get big enough sample sizes. Or to weigh their importance against eachother. I'm not saying you can't make stats like these, and indeed there are stats out there that try to do this: Baseball Prospectus' Deserved Run Average (DRA) is one. It adjusts for park, league environment, batter (quality and handedness), catcher, umpire, defense, temperature, pitch types and anything you could imagine. And it does have a better predictive value for future ERA than FIP, and of course far better than ERA itself. (However I don't think that'd go over well on this website, as it has Oliver Drake as the 4th best pitcher on the Brewers behind Perez, Hader and Peralta, making the Drake haters seriously question its validity )

A stat like FIP is simple, easy to caclculate, has good predictive value, and is easy to understand. High K% and low BB% tends to give up fewer runs than the other way around. It does a good job of isolating what the pitcher alone can control. But doesn't account for how the pitcher interacts with the park, the weather, the defense or quality of contact. Adding these things onto the stat is the hard part; even something seemingly as simple as quality of contact. Is it exit velocity alone, or based on EV combined with launch angle? How does in which direction it's being hit factor into it? And is a hard ball hit into the shift any better or worse than a weak one away from it? Average EV or median? Distribution of artibtraily decided soft/medium/hard %?

What I'm getting at I guess is that there's a choice between precise but limited (FIP) or imprecise but extensive (DRA). DRA is already good, and will likely improve. But there's the problem of not really understanding what the number means. It's like a black box spitting out a number, but you don't know how you got there or what it's based on even if it's accurate. To take an example: Knebel has a 3.38 ERA, 4.38 FIP. Houser has 1 ERA, 2.76 FIP. They have the same DRA (3.20 vs 3.29). Now in that particular case it's likely to do with leverage/quality of batter and HR/FB rate (Knebel isn't going to continue having 40% of his flyballs go for HRs, nor is that going to stay at 0% for Houser), but that's because we know these other stats. It's an improvement, it can at a glance compare pitchers both in results and with some predictive value. But since you still need other context to understand it, it doesn't offer as much beyond (x)FIP as you'd hope.

So it's a bit like the greatest supercomputer in the universe spitting out "42" as the answer to the great question about the meaning of life, the universe and everything. Great, but what is the question?