Do It Yourself

The 1910's style (not 1940's 🙂) is a matter of taste. If you don't like it you don't like it. But there are actual advantages to it:

• The lenses are closer to your eyes, providing a huge viewing port with small lenses, limiting chromatic aberration with high index lenses, making lenses thinner with high Rx lenses and making smudges and dirt less visible.
• The frames are narrower, making them less susceptible to damage.

But if the style puts you off, clearly that's a personal preference.

As for your other points:

The frame is by far the cheapest part of a pair of glasses

Depends on the frames. Some are stupendously expensive.

it needs to be durable (this one is not and can not be)

How do you know? Have you tried them?
I wear them every day all the time. They're perfectly durable.

UV resistant (PLA isn’t - why not at least use a better filament?).

My everyday glasses are printed out of PETG, which isn't affected by UVs. My reading glasses - which stay indoors - are printed out of PLA.

But it doesn't matter: if your PLA frames become brittle, no problem: print another set, mount the lenses and off you go. It takes 30 minutes at the most.

You’d think that a proof of concept like this would at least try and make use of the unique advantages inherent to 3D printing to come up with a design that isn’t possible or economically feasible with mass-produced glasses, but there’s none of that here

You totally miss the points of those 3D-printed glasses. They're not a proof of concept and they're not a way to save money on the frames.

What they provide is freedom from opticians. If you break your frames - assuming you didn't damage the lenses obviously - you just print new ones and you resume your life in 30 minutes.

When you rely on an optician, you have to go there (without glasses obviously, good luck driving without glasses with high Rx lenses), order new glasses, often choose new frames because your old frames conveniently don't exist anymore, or the same model is slightly different and your old lenses don't fit them, then you have to wait for days or weeks for the glasses to arrive. And while you're waiting, you have to live without glasses.

Not to mention of course, the frames may be cheap, but if you go to an optician to have new glasses made, more likely than not, you'll need new lenses. That is NOT cheap.

My glasses make me independent from all that. I don't need to wait for new glasses, and I don't have to pay for new lenses if mine are still serviceable. If I sit on my glasses, I get up, fire up the printer, clean the prints a bit with fine grit sandpaper and/or acetone, mount the lense into the new frames, install the hinge pins, and before my wife is done cooking dinner, I have new glasses without ever leaving home for zero dollars.

That's their appeal. Not the price or making 3D-printed everything for the hell of it.

That's also why - as you noticed - I put a lof ot thought into them: I LIVE with them FOR REAL.

I would personally rather trust a professional to fit glasses to my head instead of winging it myself.

You are very wrong about that. The professional is valuable to measure your pupillary distance and vertical angle, and make sure the lenses sit where they should. But glasses that are meticulously customized by yourself to fit your own face are the best glasses you can get.

There's nothing magical about fitting glasses to a person and opticians don't really want to do the final fitting: it's long, it's not optical work per se and they're rather send you on your way asap. When you do that yourself, your glasses will be as good as can be.