It is a mixture of more things. Just because Covid hasn't probably impacted you guys financially, doesn't mean it hasn't done so with other people. There are around 83k season tickets for Camp Nou. The waiting list for getting one of those is very long. At the start of this season, Barca offered those 83k to pause their season ticket for one season if they are impacted by Covid and literally "can't afford" them. Nearly one third of those 83k have taken this offer, which tells you a little bit of how hard Covid has hit people in Catalonia.
Another thing is lack of tourism. Passenger numbers at airports are still less than 50% of pre-Covid numbers. Asians especially have issues as their vaccine isn't "allowed" everywhere in Europe. Don't know about Spain and Catalonia in particular, but can be a factor too.
Prices for a ticket haven't changed much and other Europeans are hit by the pandemic too. I'm sure there is a significant smaller pool of Barca fans who can afford a journey to Barcelona. Ticket prices for the Clasico start at €99 which is a lot (I know, it is a Clasico). On top of that you have to wear a face mask in the stadium, which lowers the fun of the experience too.
Of course, performances on the pitch matter too and might play a role too, but I doubt it is the main factor for a lack of visitors. The club had worse times when it was much harder to get a ticket for the Clasico than it is now.