I would like to, but... have you tried to use thunderbird on an "older" linux laptop nowadays? Even with 8 gigs of ram, and a non-fancy memory-saving windowmanager, thunderbird is almost unusable now (large imap mbox), firefox even worse. I don't see why all that additional bloat is needed, or wanted. Please keep in mind, that a lot(!) of people are not able to afford buying new hardware every now and then anymore. And this is getting worse. First the pandemic, then the war in Ukraine, now the war in Middle-East. Shortage of ram/storage/everything (thanks ai) and massivly increased costs of energy, housing, food, insurance, everything. And in the years to come, I am afraid, that will be getting worse. Please think about it, when adding the "next cool feature", 'Keep the internet affordable'. --thunderbird user since 1.0

Regarding FF: Something is probably wrong with your install, or the websites you have open.

As a datapoint: FF + Chrome with lots of stuff open uses 2.6GB on my machine. With XFCE and a GB of other apps, it’s using about 4GB. 15 year old machine. Perf is fine.