Some connections between lines in the Barcelona Metro network are virtually instantaneous, some others are quite short, some are long, and then we have, in a category of its own, the one in Passeig de Gràcia. I do not know what you do, but I avoid it whenever I can. I prefer not to walk the equivalent of three blocks of the Eixample on a narrow tunnel..
Perhaps you don't know that the tunnel where we walk nowadays to connect between lines takes up part of an underground car park, which is actually behind just a wall of separation. Specifically, we walk along its second basement. If we could get through the car park, the connection would be a little shorter, but the parking was inaugurated in 1967, before the construction of L4, and the best solution they found was going along ots edge.
In order to reduce the distance the existing underground halls would have to be modified, and some new entrances would have to be done, in addition to a new corridor, that would go below the parking lot. Due to its cost you can imagine that this project is waiting for better times.
I think we'll still have a long connection distance for a few years.