I absolutely see what you're saying. That the experience of having a college life, the camaraderie inherent in college basketball, the excitement of a Final 4 run ... Those are things that aren't replaceable.
But you know what else isn't replaceable? A normal childhood, instead of going to a basketball academy or being homeschooled from 10 through 15 with the intent to entirely focus on basketball.
And then when you're 15 going and playing in a foreign country (Spain) where you don't speak the language. Staying there long enough to build connections, and being promoted to the top team with a real chance to win Eurobasket, a truly unique and meaningful experience with teammates you know and love ... and then leaving everything you know (again) for the next developmental step (NCAA basketball).
If it was me or my kid, I would absolutely advocate to stay. But I also wouldn't push my kid to homeschool from 12 or move to a foreign country at 15 or another foreign country at 18 to keep taking on bigger challenges. I'd push more for my kid to be a kid and have a somewhat normal childhood...and that (plus genetics, talent and probably some other factors) is why my kid isn't going to be a Demin quality player
The advice I'd give him would never have gotten him to here to begin with