Pedri and Busquets were bad choices and he was too slow to react and change
Other than that, well, that's the quality of his team. If Messi isn't a monster, that's just not a great side. Lots of very good youngsters, but they're youngsters still. They still look better than last season, more compact and less vulnerable
Busquets is done at this level, and in all honesty while he was still a great player in the MSN years, that's one player who got to perform in ideal conditions for years with Xavi and Iniesta and it's clear he never would have been that good in a different context(tbf, that goes for a lot of great players, but Busquets has been widely seen as an all time great, and individually he just wasn't, ever)