Although I know what T-ski is getting at about "turning the band around musically," honestly, when you step back and look at the catalog objectively, the answer becomes a lot murkier. Although I'll give my opinion at the end of the post.
With DeGarmo, the band had a songwriting evolution. People may not have liked that evolution, but you hear a progression of songwriting from the EP-HITNF, and again with Tribe (particularly the songs that featured DeGarmo as a co-writer), that sounds like the same band. To me, THAT is Queensryche, that progression of songwriting that came in the form of DeGarmo and Tate, with a strong third man in Wilton in the 80s (and less so in the 90s). Rush is a band that very much changed throughout its 40 years, but still sounded like Rush. Queensryche, in its original form, was doing the same.
Opinions vary of course, but for my money, that continued evolution and the distinctiveness of those five guys and what they bring to the table (Scott has a very distinct, Rush-inspired flavor to his playing) really is "Queensryche."
When Geoff was fired and Todd was brought on, I think it's pretty notable to see that La Torre/Wilton wasn't the mainstay of the songwriting. It's VERY spread out. Eddie and Scott took a much larger role, and Parker, now, has grown as well. In a way, the band has de-evolved back to the early 90s, and has started forging a new path from Empire.
And I think that path has less to do with Wilton (who again, his playing, riffs and leads are very distinct and a key part of the QR sound), and more to do with La Torre helping frame the direction a bit. I mean, if you've heard his solo album, you see the metal he is capable of, so he's reigned in a bit in Queensryche to focus on that melodic, psuedo-progressive hard rock sound. But he's also said a number of times to me in those first few years of being in the band "that's too heavy for Queensryche." So in a way, I think it really has been La Torre who has been pushing the band to get heavier and heavier, but being conscious of that fine line of who Eddie and Michael are as players and the back catalog music.
In short, I'd say it is more La Torre's joining than Tate's firing that has pushed QR to where it is musically. I don't really hear a lot of songwriting evolution from Wilton. His riffs and leads are very much what he's always done from 1983-1990. And that's not a knock on Whip at all -- I'm just saying he is who he is as a writer and a player. Eddie has injected some more songwriting, and Parker has a little, but in total, to me, it's La Torre injecting his creative presence which has steered the band down the path they are now.
When you hear a Whip lead, there is this whiff of classic Queensryche. But other than that, it truly sounds like a different band to my ears these days. And that's not a criticism, that's what they should do. But if you like what you are hearing, I think the credit has to go to La Torre, as opposed to simply firing Tate. Had the band gotten a non-musician singer, I'm not sure they really would have gone down the path they have.