I agree that it would probably be nice if those could be turned off, and the UI is sluggish, but VC6 was (apart from being fast) not much to write home about (compared to what we have now).
Anyway, this is is just 1 contrived example of something modern OSs do, and that OSs from the 90's didn't do.
Sure, there's some bloat, but a lot of it is the "Mozilla kind": "Mozilla is big not because it is full of useless crap. It is big because your needs are big".
Just booted my laptop (FreeBSD -current amd64, 1366x768 display) and started X: only 204M "Active" memory. Of the 204M: 60M is syncthing, 39M compton, 31M Xorg, 11M i3bar, 11M polkitd, 10M i3, 9M dunst, 5M wpa-supplicant… Not counting syncthing that's 144 megabytes. I think that looks reasonable. You can go lower and optimize for low memory (no polkit, no compton — 94M) or go higher and optimize for usability and fancy UI features (install gnome :D)
Let alone USB. During my training, there were lots of desktops running Windows NT 4.0, which did not know USB. By the time I had already become so used to copying data back and forth with a USB thumb drive (even though back then their capacity was still measured in megabytes), that it became fairly annoying to walk up to some computer, plug in the thumb drive, then realize this machine is running NT 4.0, not Windows 2000, cursing, then looking for another way to get some piece of data on that computer: Usually put it on some other machine copy it over the network.
Ah, those were the days... ;-)
This doesn't add anything, because contrived or not, it doesn't answer the question that was posed: "What does modern Linux do that Solaris from the 90's did not, that it requires 50x more memory?"
It hits the first part of the question, but not the second part. We could add wifi to a 90s OS without severely inflating the memory requirements. My Nintendo DS (with 4MB RAM) "seamlessly connects and disconnects to wireless networks", after all.
You could easily answer the question with a sensible, non-contrived answer, and I'm not sure why you didn't.
I recommend everyone to try and build an LFS (Linux From Scratch) at least once or at least set up an ArchLinux box to get a feel for how Linux actually works and where the bloat is.
As an example, the music player daemon (MPD) has 110 dependencies among which is wayland or x-org, I don't know why.
Also, using udev to only load needed kernel modules helps with a lot of memory usage.
Also, if you'd like to compare performance degradation over time, NixOS is a good choice to run because it can simply rollback to old configurations and you can see what changed.
I have small Linux systems today that work comfortable with 128MB of RAM used.
What my modern linux system does that Solaris didn't do in the 90s: runs a browser than can render absurdly detailed scenes using OpenGL where the object model itself exceeds 1GB (it fits nicely on the graphics card, but the computer is also loading that from the net at gigabit speeds and storing another copy in RAM).
That said, I think it's true that modern systems just waste oodles of resources unnecessarily.
It's salutary to consider that the memory for a reasonably spec'd machine a little over 20 years ago is now a rounding error
I remember at about that time having 80MiB of RAM: a) my machine flew, and b) plenty of people would ask why I needed so much
When we have less, we make due with less. When we have more, we consume more. It's sort of like money.