Technically 3.5" SSDs are still out there, but they’re massive (16-64 TB) and target enterprise use (with a price to match).

And 3.5" is still the standard for platter HDDs, which are still the more economical option if you need large amounts of storage.

Now if you meant no more 3.5" floppy disk drives, then yes, those are definitely gone. ;)

I think you may have misread OPs post. They haven’t built a PC since shirtly after they were 10-11, which was almost 30 years ago. So developments since the turn of the century are in fact relevant here, heh.