I also haven't been to Barcelona since about 2017 and the food scene there is so vibrant that I'd probably look for recent recommendations. This site usually is trustworthy (though I'd skip the Asian recommendations):
https://www.eater.com/maps/best-restaurants-barcelona-spain
Dinner is very late in Barcelona for locals. I seem to remember a lot of places don't even open until 8:00 pm. Unless it's a really hot place, showing up when they open will probably get you a table as long as it's not a big party.
Given the crowds in Europe these days, if there are any places you really want to be sure to go to, I'd try to reserve in advance.