I really wish it wasn’t online-only and closed source though (same as figma I suppose)
And the grid-oriented working method isn't ideal for me, though I confess I've not gone back to look at TinkerCAD much since learning OpenSCAD and FreeCAD; it may be that a better-informed visit would show me where I was judging it too hardly.
But it is amazing what people do with it, and while I have my issues with AutoCAD, it's clear that TinkerCAD is a truly liberating tool for an enormous number of people, and my criticisms may be getting into gift-horse-examination territory.
I just needed to make a couple adjustments to an STL this week, I haven't done any CAD in months, in principle I have used Fusion before and had a nice experience with it, but since it's been a while I don't remember any of it and would have to look at some reference to get back into it, with tinkercad I could just drop the model in and make the adjustments I need by playing around with the shapes they provide. It didn't feel very "precision engineering" like but sometimes it just needs to be close enough.
It's also arguably better at hacking on STLs than a bunch of higher-end CAD packages; it feels like that's been a focus of their efforts.
Personally what I'd really like to see alongside it is a sort of Scratch-blocks-based OpenSCAD/Build123D type thing -- this may already exist?