Sicario2 - Tier 1 ordinary players aren't going to shift the needle for us. And at this point, we clearly no longer have the capacity to spend money freely (at least not until we improve outgoings).
So our task is to bring in top players (or players with top potential) who aren't over-valued (of which, Calafiori seems to fit that mould). Sesko also fit those criteria, but the CF market is even harder to recruit in given paucity of supply. Basically, it's not that easy to make the signings we need to improve.
Additionally, assuming we can only improve by bringing in new players misses the point of our whole squad building approach - most players are either improving or hitting their prime so you'd anticipate an organic improvement YoY, notwithstanding our YoY tactical evolutions as a team.