If we follow this line of thought, Chelsea shouldn’t have bought Drogba and Calvahro and Barce shouldn’t have bought Deco.
I don't know that works because Deco and Carvalho were at FC Porto, which is an established upper crust club with a good track record at developing players they scouted & that squad specifically just won a C3 and C1 back to back IIRC.
Drogba moreso, spent a lot of time in Le Mans before quickly ascending through Guingamp to Olympique Marseille where he has a big season even losing a C3 final there just like Fiorentina did last year (UEFA Cup was arguably a tad more relevant then).
No dig at OM or Fio there, they're legacy big clubs in their respective leagues but Porto has a track record as a common step towards joining a top club afterwards.
Overall I agree with you but it is perhaps true that it is rarer today for a good prospect to not be enrolled early by clubs making up the pyramid leading to the top.
That said... Feyenoord is not a nothing club, neither is Club Brugge. That Hellas loan coincides with the club doing a good campaign in their first season back in Serie A. Reportedly -though transfer rumours are what they are- Sporting CP were interested in 2018 and FC Napoli in 2020.
At the rumoured level of fees (30m£) expected it's a good gamble for a player known to be an hard worker.