See the sibling comment for why this "solution" is a joke. Also keep in mind that takeout is completely buried so fewer than 1% of the users know about it, let alone use it enough to not get screwed by a lockout of their most recent data.
Compared to "takeout" permanently forwarding mails is better. That way you always have 3 copies. One in gmail, outlook, and apple. Well hope you don't screwup so much that all of them block you at the same time.
Well also less than 0.001% of the users accidentally lose their account and don't get it back so.
That’s still a manual, non automatable backup. To have any reasonable backup strategy you’ll need to find something service by service, giving up some that just have no API nor compatible query language (I think keep is part of that, you’ll have no way to auto backup)
Then I'd need some other software where I could start a server and import my data. Otherwise it's useless.
If this software exists and it is an adequate substitute to Google products.. well, let's just use it then.
It's relatively time consuming to do this. And how often should I do it? It's not as simple as the name suggests.