If any of Oklahoma, Ohio St or Clemson fell to also-ran status, you'd be left with a pretty weak conference.

In the Big 12, it would be lots of talk about 'maybe this year Texas makes it back' and then a couple other programs (Oklahoma St, Iowa St, etc) that have their ups and downs of being relevant and provide a decent second tier.

The ACC is maybe worse without Clemson. North Carolina and Miami having to carry the weight, but not a lot of national relevance.
Big 10 minus Ohio St is a bit stronger, based mostly on Wisconsin. Michigan and Penn State fall in the Texas role of once-great, but now struggling team, Minnesota and Northwestern and the like can be the teams that occasionally rise up.

If one of USC, Oregon or Washington would really step up, you'd have that team as the national title contender, the other two as the sleeping giants (see Texas, Miami, Michigan etc) and then a tier of teams like Utah and the Arizona's as teams that can occasionally make some noise. Getting one team back to nationally relevant fixes a LOT (not all, but a lot) of the issues with the PAC12