That is pretty standard in most Fortune 500, whose main business is not selling software, and most development is done via consulting agencies.
In many cases you get assigned virtual computers via Citrix/RDP/VNC, and there is a whole infra team responsible for handling tickets of the various contractors.
Similar story at my prior job. Heck, we still had one package that was only built using 32-bit .Net Framework 1.1. We were only just starting to see out-of-memory errors due to exhausting the 2 GB address space in ~2018.
I love the new features of .Net, but in my experience a lot of software written in .Net has very large code bases with a lot of customer specific modifications that must be supported. Those companies explicitly do not want their software framework moving major supported versions as quickly as .Net does right now, because they can't just say "oh, the new version should work just fine." They'd have to double or triple the team size just to handle all the re-validation.
Once again, I feel like I am begging HN to recognize not everyone is at a 25 person microservice startup.
I might be missing something but the combination of 'we mustn't break anything' and 'we can't test it without 2-3* team size' sounds like release deadlock until you can test it..
The migrations where I've worked at have always been a normal ticket/epic. You plan it in the release, you do the migration, you do the other features planned, do the system tests, fix everything broken, retest, fix, repeat until OK, release.
Otherwise you're hoping you know exactly how things interact and what can possibly have broken, and I doubt anyone knows that. Everyone's broken things at first sight seemingly completely unrelated to their changes at some point. Especially in large systems it happens constantly. Probably above 1% of our merges break the nightly in unexpected places since no one has the entire system in their head.
Or you're keeping a dead product just barely alive via surgical precision and a lot of prayers that the surgeon remains faultless prior to every release.
In many cases you get assigned virtual computers via Citrix/RDP/VNC, and there is a whole infra team responsible for handling tickets of the various contractors.