I would leave it alone for this year. Perhaps a good mulch with some stable manure or your own compost and a dressing of bone meal for a slow feed.

you often get thick and thin stalks, that's the nature of the plant.

Give it time and some will be thicker next year. Just be patient and give it a good feed now and again.

Thanks J, I wish I’d left it alone as it’s been really productive for several years.

I think the thin sticks have something to do with the very dry Spring we had. Mine are the same - wanted some at lunchtime and there were none fit to pull. I'm going to give it a feed wsith a general fertilizer, probably Miracle grow because there's some on the shelf. Also make sure it has enough water, which is what I didn't do as even carrying a canful raised my BP too high...
So sorry, I know how frustrated you'll be So am I.

Thanks for that suggestion Sue, I too have miracle grow in store. But I did give the rhubarb a canful every day during the dry weather.

Did you? Maybe if I'd done it as I should it wouldn't have made any difference then. You have comforted me a lot!