Surely, they are a huge asset to your team. But wouldn't you be delighted if you had turned them into regular BBBL starters ? After all, I also thought that a 18-yo trainee wouldn't fit in a team tailored to get results, but now I think I was wrong, and it is doable (though not always simple, that's for sure) to craft a player from scratch to suit your requirements.
Not to mention that with time passing, your trainee slowky turns into an acceptable sub, then an acceptable starter ... then an acceptable world class player, if there is enough dedication AND luck with injuries, of course.