(If anyone knows of a tool that helps me rapidly clean up my gmail, please let me know).
But the worst thing about email is that nobody knows how to write emails anymore. Everyone just quotes the while thing and adds their comments on top. People no longer trim down the email and intersperse their comments throughout the response. Mail reading software no longer aids you in doing this - cleaning up the quoting for you (not that many mail readers did this before).
And when you don't want to quote the email you are responding to, people include the whole mess anyway and just pop their response at the top. Rather than understanding that a threaded mail reader (as most mail readers are today) will provide the reader with the context they need just fine. There's no need to repeat dozens of older responses.
I miss email from 25-30 years ago. When 90% of what landed in my inbox was actually for me, written by other human beings. Most of which knew how to produce a response to an email without it just being a sloppy mess.
I wish people who wrote mail clients were more intelligent product designers and more thoughtful people. That they would understand that catering to people's poor habits was, and is, a bad idea and that a better idea would have been to make proper email quoting at least a path of considerably less resistance.