I mean what do you replace it with, return to the prior status quo of private security? I don't think that's even a good idea, and I dislike the TSA as much as everyone else - nor do I think having Local LE do it makes sense, because then you end up with 900 policies.
As far as I know, the US was among the last countries to adopt what other countries did, which was have some sort of federal police perform airport security.
Also, I fly pretty regularly - about one round trip a month - I find the TSA folks pleasant to deal with, and generally courteous - but I also know I'm an actor in a play, and I need to go thru the motions like everyone else.
Functionally, TSA is about 50% theatre, its meant to make Bob and Eileen from Cedar Rapids who fly twice a decade feel safe.
https://news.ycombinator.com/item?id=37624112