Counter-argument time.
1/ I'd argue that understanding squad status and playing time is more important than talent or potential. Nolito's a really really good player and more importantly he knows the Barca way.
2/ He's obviously keen to come back. Probably at the time in his career where he just wants to win some medals.
3/ He will be 30, but for now, he's 29. Plenty of our squad are that or older and performing well. We're talking about a backup player here, all we need is 2 or 3 good years to be a success.
4/ I'll remind you guys Villa left at 32. After his injury, he still performed relatively well up to when he left (also at Atletico). Again, 2/3 good years until the next crop are there.
Guys like Sane, Brandt are undoubtedly talented, but we've got the best front 3 ever, it's just about keeping the squad harmonious. Few years on we'll be looking at starters.
That said, I wouldn't mind someone else (Sane may be a bit pricey), just hope it's the right fit.