I think they're building fairly well (but not earth shatteringly so) under Luis Campos. Donnarumma could be keeper for the next 10 years and, although he hasn't become the absolute beast people expected, is still very decent. In defence, Nuno Mendes and Luca Beraldo are top prospects while Hakimi is only 25 and Lucas Hernandez is 28 with Mukiele and Kimpembe as solid rotation options. Marquinhos isn't what he was but isn't ancient at 30 while Skriniar is a year younger. I was surprised that Ugarte hasn't really been in the team as I rate him highly. Moscardo looks an immense talent. Zaire-Emery could easily become the best midfielder in the world one day while Vitinha has been amazing during the season just gone. Up front is where they are weakest now, especially with Mbappe going. Muani has flopped somewhat. Ramos was better but didn't exactly light up the place. Barcola has a ton of promise. Dembele is a wildcard but I like him. I'm not wowed by Kang-In or Asensio. They need a CD and two great attackers long term.
I'm not totally convinced by Luis Enrique as a coach tbh but he'll do for now.
So no, I wouldn't say it's a failed project. They've raised their profile immensely. The CL is always the priority for them and they're probably further than ever now but I do like what they're building long term.
Future team (25 and under) -
Donnarumma; Hakimi, Mendes, NEW, Beraldo; Moscardo, Zaire-Emery, Vitinha; NEW, Barcola, NEW
Get in Leny Yoro, Desire Doue and Victor Osimhen and they'll be scary.