I agree with you generally. I think we should not write off Dele.
I have my doubts about how/why would he start blossoming again under Poch (he will support, defend and pick him whatever happens) but I think under another coach, some fresh perspective, feedback and instructions he has every chance to regain the form.
Though this point of yours "who has done XX and YY by age 23 or 21" is absolutely and 100% irrelevant. Players developement curves are different. And some might as well be still bench-players at 21 and go step by step, become better and play until being 35. Others can peak at 21 and be finished by 26. So it does not make anyone better or worse what they have done by some random age number. By the end of 2005-2006 Ronaldo had only scored 32 goals during his career and he was 21. Mbappe has 89 goals and he has few months to go to his 21st bday. So what? Does that mean that Mbappe was, is and always will be 3x the player that Ronaldo was and is? Or well, can it be just that he was early bloomer and his greatness comparison to Ronnie could wait until both of them have finished their careers? I personally believe the 1st option to be true.
The age reference is entirely relevant given that it's commonplace for young players to dip in and out of form. Many factors that influence this but IMO just isolating for a moment the top players in this bracket (young players playing in top teams that contest title races, semi-finals, cup finals, their Snr International side) there are two:
1. Having to learn new facets to their game whilst still learning their core ones. With the level of analysis available to opposition scouts, players have to evolve or else they are nullified through tactics, be that doubling up on a player or cutting the supply to him etc..
Dele has played at the left of a diamond, the base of a diamond, at the tip of a diamond, as 2nd striker as main striker and as a number 10, 4-4-2, 4-2-3-1, 4-1-4-1, 4-3-3, 3-5-2 are just the formations we've deployed under Poch the last 5yrs. Within these formations and positions, he's been asked to perform different functions from leading the press, to having to drop deeper in a mid-block as we dropped our high-press lat 2 seasons.
2. Doing this as a young man, in the spotlight of the Worlds media. Imagine George Best in today's game, he would have drunk himself to death by 24, IMO no way he would have made it under today's 24/7 spectrum of social media (he was 28 when he left Man U already serious questions about him had been asked from the age of 25yrs old, just 1yr older than Dele is now!!!).
Loads more nuanced reasons and many we will never know about but are simple as just turning from boy to man is as simplistic as it comes. Just splitting up with a serious relationship might affect something, and if it affects Jonny from accounts or Jack the chippy then it also effects Dele the superstar footballer.
