I think the main problem is actually the lack of an SSD. Opening programs, files and compiling takes just forever.
I showed this to my boss but he just thinks it's not a big deal.
Possibly just replacing the spinning rust with cheap SSDs might be a good compromise. Modern laptops have a separate M.2 connector, but these old ones probably don't.
Another solution might be to have a single central server to stand up docker instances fast, if that's a thing you need.
Also, maybe look in to using something like raspberry pi 4 as an extra plug-in unit to help out (as docker host)? They're surprisingly powerful; possibly at least as good as the 2011 laptops. At least try one out and see!
... and you're spoiling these guys ;-) Back in my day, I used notepad and javac raw, and liked it!
Maybe devise a test which you can do with your boss? Write down 10 common tasks and try them out on one of the computers.