"My question is, should I now plant cloves from these pitifully small
bulbs, hoping that genetics kick in, or will they only produce an
inferior crop?"

Yes, and yes. The genetics are still there, but it will probably take a couple years - under good conditions - before they regain their previous size. If you still have access to your original source, though, and want good bulbs this year, then you might just want to start fresh with good stock.

Most of my garlic varieties were stunted in 2015, due to excessively wet weather, and poor drainage. Some of the soft neck varieties only produced a round, the same size as the clove I planted. Last year I moved them to a better-drained location, and they regained about half of their size... since the cloves were close to normal, I am hopeful that the bulbs will be normal this year.

Thank you both for your replies. Unfortunately, I didn't save the bulbils, so that's out.

Think I'll bite the bullet and buy some new stock from my original supplier. (If his crop pulled through OK!) Don't want to wait 2 years.

I only plant around 100 each year, so not a huge financial outlay...

Were the cloves small inside the bulbs? If not, but simply fewer, then plant your own back. IIRC it is clove size rather than bulb size that determines the following year's outcome. I would probably not replace a strain with a locally successful history over a number of seasons, at least not completely, simply on the basis of one less than completely successful crop from exceptional conditions. What you have has proven to survive and produce under a variety of conditions.

^^^ Was thinking about this yesterday while washing dishes.

OldDutch...yes, the cloves were not fewer in number, but were very small, proportionate to the size of the bulbs.

The guy I purchased my original stock from grows his just a few minutes drive away from me, so they also have a successful local history. He's been growing them for several decades.

Might plant of few of my smaller ones nearby to see what happens...