I might sound like those weird language evangelists, but...
> we could be writing all our programs in C, still.
You don't need to use C, there are other languages. For example a hello world in Free Pascal[0] (a natively compiled language with no runtime or other dependencies, which supports object oriented programming and has RTTI rich enough to implement automatic object serialization, semi-automatic memory management, strings that know about their encoding, etc) is just 32KB.
Some time ago i wrote Fowl[1], a mostly complete recreation of the OWL toolkit that came with Turbo Pascal for Windows, the demo program of which is around 80KB.
Of course for a more realistic (and MUCH easier to use and develop with) approach, you'd need something like Lazarus[2]. A minimal application in Lazarus is 2.18MB. This might sound too big... and TBH it is, but the size doesn't grow too quickly from there. For example a profiler i wrote recently for Free Pascal applications is... 2.16MB (yes, smaller, why? Well, because i replaced the stupidly huge default icon with a smaller one :-P and without the default icon a minimal application is 2.05MB so the profiler added around 100KB of additional "stuff").
> It's doing autocomplete suggestions, linting code as I type... all sorts of things we never had a couple of decades ago and are huge productivity boosters
FWIW we had those, Visual Basic (or even QBasic) would format your code as you type it, Visual Basic 6 and Visual C++ 6 would profile auto-completion (VB6 even for dynamic stuff), etc. Only issue with C++ was that sometimes it wouldn't work around complex macros.
But modern editors do a bit more, still no excuse for being that sluggish. Lazarus does pretty much everything you'd expect from an IDE with smart code completion (e.g. things like declaring variables automatically, filling method bodies, etc) and code suggestions yet it runs on an original Raspberry Pi.
Now i'm not saying that you should not be using whatever you are using or that you should code on a Rasberry Pi or even to switch to Free Pascal / Lazarus (which honestly is far from being free of issues), but i think that you're overestimating what tools do nowadays and many people are so used to running slow and bloated software that take it for granted that things should be like that and cannot even imagine things being better.
[0] https://www.freepascal.org/
[1] http://runtimeterror.com/tech/fowl/
[2] https://www.lazarus-ide.org/