I have PreCheck, first due to my frequent traveler status with my (at the time) favored airline (which, as I understand it, PreCheck doesn't offer any longer) and then as a paid member, when I noticed that over ten consecutive entries, I was redirected to the non-PreCheck screening side 8 times (it now happens much less).
When I fly out of Houston's IAH (Terminal A), I routinely get mixed into the same screening area as non-PreCheck travelers (after a shorter line for the travel document checks). I show my boarding pass on my phone or my watch with the little check mark when I enter the screening area to an agent that never scanned my boarding pass, nor have they been in communication to the agent who did scan my boarding pass. They visually check that the checkmark logo is there, then orally call out to the machine operators that I'm PreCheck, and I don't have to take out my laptop or take off my shoes/jacket.
I also got grandfathered with a tiny membership rate into the CLEAR program in its current (second) generation, a program that doesn't hide its commercial status at all, and says clearly "pay for this and you'll have zero wait". I get to IAH Terminal A, tell the CLEAR agent I'm a member, and they quickly computer-scan my pass and verify my fingerprint. They walk me to the TSA podium, flash their CLEAR ID badge, and tell them my identity and boarding pass was verified (and that I'm PreCheck, since my known traveler number is associated with my CLEAR account as well). One more quick scan of my pass and I'm through the longest part of the wait: waiting for them to check my ID. I'm through security even on the busiest of days in about 15 minutes, mostly in 5 minutes. I know the wait time would grow again if everyone had CLEAR, but the ID verification part would be super fast.
Security lines themselves only seem clogged up by people who don't follow the rules (because they aren't frequent travelers) or who object to them. I don't agree with the rules, I write my congressperson to object to them, and I'm embarrassed by them when I'm speaking with people who don't live in this country. But until my letters to my congressperson (the method by which "We The People" can actually influence our government) are joined with millions more, security theater will remain.
CLEAR showed me that ID verification with PreCheck (since they have your fingerprints anyway) could be quick and efficient. It isn't. Some US airports have security lines that move quickly even in the busiest times, because agents are helping passengers comply in advance with rules with which many travelers are unfamiliar. So it can be better there, too.
But to effect change in our government, we have to participate in our government, which goes beyond voting every four years; it means writing to the representatives you or your neighbors have voted into office.