Texas was in a rut from 2010 to 2017. That's when BYU and Cal beat them. Texas is a perennial top 15 team. Just like the other programs I mentioned.  The pac 12 doesn't have that. They used to with USC. Without that, the pac 12 will never be a serious contender in the CFP. Without being a serious contender in the CFP it's simply the P4 plust the pac 12.

Let's be honest for a moment. What is the draw of P5 membership? Money and championship access. This is the reason why, if BYU makes a best of the rest conference, it still won't be a power conference. They won't be granted access. As it stands the PAC 12 technically has access but they have to have an undefeated team to beat out a 1 loss champion from either the Big 10, Big 12, or SEC. Now with clemson dominating you can add the ACC to that list. Clemson is in with 1 loss over any PAC 12 champion with 1 loss. 

Imagine every conference having a 1 loss champion. Who gets left out? The PAC 12.

Why?

The P5 hierarchy goes SEC>BIG10>ACC>BIG12>PAC12

You could interchange ACC and big 12 most years but since clemson is dominating, they get the nod right now.

So while the PAC 12 has access, the hurdle it has to clear is far higher than any of the other P5 conference.

To tie this all back together: It's not a coincidence that the year the PAC 12 got into the playoff, texas and oklahoma were down. If the PAC 12 wants to be a serious contender they need USC to get back to one or two loss seasons. Then the team who beats them will get in or they will get in. Until then it doesn't matter how good the pac 12 is. They won't sniff the playoff without help from other conferences in the form of losses.