While it’s sad to depend on a web service that could be gone tomorrow, it’s not like we really “own” software installed locally either. License agreements contain the phrase “the software is licensed, not bought” for a reason.
For example the software I sell in my day job has an expiration date of a year, there is no perpetual license. It literally won’t start after a year. The difference between that and a web service is pretty slim.
It's not. Ask anyone working on MMO server emulators. Once the server is gone, that's it. With thin browser client you might as well create a new CAD software from scratch. Having actual software on pc means you can at least attempt to crack it.
The renting part is the same for fusion360
Unfortunately, there are no (major) CAD programs you can own outside of FOSS.
Solidworks is still available to buy as a perpetual license -- pricing starts at $4200 for Standard. It costs $1500/yr for "maintenance", but that's optional if you don't need updates.