Browser instances can be quite svelte. But uh... I mean... shared lib pages tend to be actually shared pages. That's why the physical memory for multiple browser instances is a lot lower.
What's more, I'd gladly pay a higher price for a richer experience. We no longer need to or should rely on ANSI interfaces. In fact, they're becoming increasingly awkward in a world that really wants endpoints to be stateless by design rather than stateful sockets.
Many people have already discarded the single socket model oh SSH in favor of Mosh. Let's also ditch the console for all but the most basic of tasks. It's not 1997, the lingering stink of proprietary rich client environments is cleansed. Web browsers have annihilated that assumption and made something truly open and pretty amazing.
I use a web browser as my core text editor and I miss emacs not a whit and quite honestly it feels more responsive than my emacs setup. I don't notice any tangible performance differences from Vim in a terminal.
We can do better.
Don't you think that maybe you are using your past environment to judge a current experience?
Visual Studio Code is based on Electron and works wonderfully. Doesn't feel bloated, it's quite fast to open and I haven't felt a slow down in any meaningful way.
I'm not imposing my computer specs to anyone (and I'm using vs code in a client machine in any case), but we have generally a lot more horsepower now and the discussion of performance might mean little for a desktop app (heck, we are running javascript on the server nowadays!).
There is also the matter that no matter how much optimization you put into something you can't recoup the cost of the fundamental design choices you went with. Choosing something with less power can solve a lot of headaches.