Version 78.11.0 ten times slower than it was 2 years ago responding to a mouse click

[stevedonato]

It is like they rewrote it in Interpreted Basic or COBOL. Disgraceful performance. I have to click 5-10 times to get it to respond to a mouse click. Even to just open an existing email.
Running Linux Mint 18.3 32GB Ram i7 CPU.
Right now I switched to Geary email client which provides instantaneous response. I may just give up on Thunderbird, sad it use to be great.
I should have never upgraded Thunderbird.
A simply mouse click (say to high-lite an email) is all local no internet required how can it NOT respond instantaneously?
Please don't tell me to re-boot or clear cache etc. I have 30+ years computer programming and have tried almost everything.
Seems like no QA testing was done on Ubuntu/Linux mint client to gmail?