Few things to remember. In 3.5 era, legally buying pdf-s wasn't really a thing. WoTC never had real webshop with full digital releases for it's entire 3.5 catalogue. That meant you were mostly stuck with what was available in physical copies, be it in bookstores or your local game store (local being strech, since not every town has one). Even Amazon in those days wasn't Amazon of today, so online ordering was also patchy at best.
So while in theory 3.5 had tons of splatbooks, availability was iffy. Even marketing wasn't there, so if something new came out, it could easy slip under the radar.
If you lived outside of USA and maybe UK, all of the above just got worse. 7 seas of internet was best option for getting books, but even then, it required a) that you know book exists and b) someone scanned it and uploaded it. Quality of those scans was all over the place, from barley legible b&w to pretty solid in color.
Even if you managed to get your hands on all the books, it was like prospecting for gold. You need to sift trough lot of dirt to find those few gold nuggets. And for what? For few broken combos that are marginally better than big 3 full casters from phb.
From personal experience, lot's of tier 3-4 classes / prestige classes are actually pretty balanced. If you have full party of those, even with all splatbooks, power creep just isn't there.
If, for some masochistic reason unknown, i was to run 3.5 today, first thing on ban list are classes from PHB, namley Wizard, Cleric and Druid. Also, fighter gets removed, Warblade from Bo9S is new default "fighter".
My list would be: Core (without big 3), PHB2, Bo9S, Complete series, Heroes of Horror (minus Archivist, that one is bonkers), Tome of Magic, Races books, Environment books (Frostburn, Sandstorm). Lot's of interesting stuff in those, bunch of options, but nothing bonkers or game breaking. Also, i would limit game to sweet spot levels (3-8 roughly) and call it a day.