I've always been polite to tsa agents, customs agents, etc because hello no one needs to get into a battle with them but my comments were to explain why it can be stressful for some people and there are a good amount of reasons why. And sometimes the tsa agents are crabby with the passenger hasn't done anything wrong and that can also lead to passenger stress.
For my new airport it's only been operational for 2 1/2 years and security was extremely different than before at the old airport because it had multiple terminals and multiple security checkpoints so I give people at my home airport more of a pass for that reason not because the procedures have changed but the signage related to pre-check has (it was honestly much more obvious previously), the actual lines you encounter and that everyone now goes through at one single point instead of being so much more spread out. But the PP is correct that big airports often come with bigger issues if not for any other reason than more people flying through them.
FWIW the tsa do make headlines for failing to catch things from guns to how people have managed to get in without the proper boarding pass as well as water bottles and other such liquids beyond what should be allowed (which leads to inconsistency which gives passengers incorrect feedback on the process) but that's not unexpected they are human just making a side point to the comment of yours I quoted.