sure, the "chicago" ui was indeed a huge step forward... but until nt4, it was still only skin deep.
even after nt4, abominations such as mfc and heritage from ms lan manager lived on. the network protocols were so poorly designed that entire companies (riverbed, et al) sprung up to rewrite them as less latency sensitive alternatives that would actually function over wans.
Windows 95-7 design did not, quite to the contrary. Unfortunately I can't find it again, but usually the link appears on any HN discussion about classic Windows design sooner or later... anyway, the point is that the classic Win95 design was consistent across the whole OS (for apps that used the standard OS controls). UI elements had clear shadows, borders and margins separating elements visually, color schemes by default assisted that visual separation and they were customizable (e.g. for those with accessibility needs). Additionally, menus and hotkeys were consistent across Microsoft apps with (IIRC) clear guidelines on how third party apps should use menus, so that end users didn't have to learn much.