Aura existed simply because Salesforce thought to be smarter than open source, well. Can't deny it though: Salesforce engineers were great on the backend, but frontend dev has never been their thing. Back then there was Angular 1 which was miles ahead. React was released shortly after Aura itself, so to say. LWC is what Aura shall have been 10+ years ago. And that ties back to what OP wrote: awful UX extremely slow bloated with JS.

Now, don't talk me about VSCode Extensions. This is the perfect example of an awful dev experience. apex-jorje-lsp.jar with a JVM to parse Apex taking GB of memories, extensions taking dozens of seconds to load (when they load) ... In fact, the only decent LSP is aer, a simple decently working Go binary rather than the monster Salesforce shipped. The one good tooling Salesforce built in the last 15 years is, to some extent, the SF CLI - which came after the `force` CLI from the same guys who built `aer`, anyway. And nowadays, people can use that with their preferred editor from Zed to Vim with shortcuts from built upon the SF CLI.

So no, Salesforce didn't do great with tooling, they just did the bare minimum waiting on the (small) community to give them the right ideas.