Tony Vargas
Legend
I don't think that's quite fair. I mean, yes, casters were generally Tier 1 & 2, and non-casters 4 & 5. But it was hardly new nor unique to 3e, worse than ever, perhaps, but only a /little/ worse than an ever that had always been pretty darn bad prior to 3e, and isn't exactly a whole lot better, now, with 5e.Tome of Battle was great. It also addressed a problem that was uniquely 3.5. It illustrated what it took to make viable martial classes in a system that inherently put martials at the most insurmountable disadvantage they've ever faced compared to full casters.
At the same time, it's a little over-generous: ToB hardly closed that gap. It took reining in casters dramatically, as well as expanding martial options beyond ToB, to bring D&D to something like parity between the two extremes.
5e, though, rebounded from that effort, and is back to something approximating the familiar 'sweet spot' and LFQW patterns. Something akin to Bo9S certainly wouldn't hurt, except by obviating the existing Fighter &c, of course.