Like so many historical claims of "declines", this doesn't really make sense.
Call it what you will. 2e, which started as a simplification/clarification of 1e, which itself was an expansion and clarification of OD&D, was increasingly creaky. The grand sweep of 1989 was undone by a flood of options that made the base system from 1974 increasingly unusable.
TSR was flooding the market with products, and what you call experimentation in your post reflects a desperate attempt to raise more money. A lot of "classic X." A lot of reprints. A lot of "return to Y." Were there some gems in there? Of course- they had a lot of talent, still. But the quality control was gone.
Call it "before the implosion." Whatever, it's cool. If your feeling on the title are that strong, make your own! Snarf out.