1. They are not locked out of it. They can make a PF and find 24+ people who feel the same way. If they can't find 24 people who feel the same way, then they are probably the only one that feels that way, so they need to adjust their mindset.
2. Since PFs can enter as an alliance of 48, it almost guarantees a fresh instance. Only very rarely is there gonna be a non-fresh instance with less than 25 players in, and I think they intend to make it guaranteed fresh later on. A fresh instance effectively means they are not affecting "random" PUGs.
3. Nobody is vetting others to enter FT; on the contrary the entire idea is to help anyone and everyone go from fresh to clear by carring them with callouts that make it as easy as possible to clear.
4. Some runs will not be "fresh prog". You might need to have "seen" a certain phase. If you have not seen that phase, you can join a fresh prog group instead. It's not rocket science.
5. Not being allowed to join a "certain phase" party is not exclusive to FT. It's always happened with Extreme, Savage, Ultimate, Criterion, etc. It's not hard to just join a fresh party instead if you aren't up to that phase.
6. You're effectively saying High-End raids shouldn't exist. Maybe what you could ask for instead is for the normal modes to 1. exist and 2. be more challenging but not be a phase prog. Extreme trials are pretty good at that really - I can take first timers through them and prog through to the end within the timer in many cases.