It used to be fine too. Busy at times yes, but SU12 and previous sim updates were on a whole just fine (not dreaded). CM slowdowns bug has been happening since spring 2023 and hasn’t ever been fixed. I suspect the real problem is there. But you can see from the dev stream that they don’t know what it is. Search for " Content Manager Download Speeds" on this linked page.
I too live in the fear of a reinstall. (I have only 30MBPS broadband)