What you are talking about are squad players and in that case, I would also say it is difficult to improve on. Depay and Schneiderlin are actually not needed as they don't feature and therefore surplus to requirements in terms of numbers. The rest are indeed hard to improve on if you are looking at squad players. Barcelona's squad personnel includes world beaters like Denis Suarez, André Gomes, Paco Alcácer, Lucas Digne and Samuel Umtiti. Real's are the likes Fabio Coantrao, Danilo and Marco Asensio. The point is some time along the lines, fans started to get this idea that teams need 2 top players in each position to compete when looking back at history, that's not the case really. There is a good reason for that, top players start for their teams, they are not happy rotating. The majority of the top teams past and present had a core 14/15 players with the rest providing cover in case of a crisis.
Your second point is correct, although I would disagree with the term "huge" as I think it is the usual hyperboles when it comes to these discussion. Anyway, this was my point anyway, the difference between us and those teams is indeed those grade A players, game changers. The likes of Modric, Bale, Ronaldo, Neymar, Messi, Suarez and co. This is why I said unless those players become available, we are just marginally improving and that margin is not worth pursuing when you take into consideration that the improvement we might get out of continuity and therefore more coherence of personnel can be of a higher margin.