I have downloaded my data with google takeout dozens of times without a single issue. Speed was very high (maximum possible for my connection) and never had a download error. I’m talking about multi-gigabyte exports of my email and my drive.

Different experience for me, ~500Gb so about 10 chunks of 50Gb (largest chunk size) that had to be downloaded by hand because of their auth. When the download got interrupted I had maybe 4 more tries, might have been more, but after trying to many times the entire takeout expired. Automating the process, and using smaller chunks didn't work at the time because of their opaque API and its auth.

I feel like this has been made a shitty experience intentionally.

I have 900gb in my account and on my 500mbps connection it took forever to download, not because of my speed but because of theirs and it just 'connection failed' at 80% many many many times and asking to relogin. It should be illegal. Not supporting just wget -c (you can use it with a lot of trouble/hacks and it's not reliable which defeats the point) is just clearly done to annoy you into not doing it.