yea, it is too early to say something definitive, and yet yzerman haters have been talking trash for YEARS. but let's go over the prospects from your cherry picked list
2019
johansson - playing 20 minutes a night in the top 4 in the nhl and looking great doing so
tuomisto - looking good playing top 4 in the ahl, could get a look later this year or next
mastrosimone - no longer with the org, looks like a career ahler
2020
wallinder - looking good playing top 4 in the ahl, could get a look later this year or next
niederbach - no longer with the organization but is starting to turn it on and could get a contract with someone else down the line
hanas - looks like a career ahler
2021
buium - our best defenseman in grand rapids most nights. will most certainly be getting nhl minutes within the next 12 months
7 prospects over 3 years. 1 of them looks outstanding in his first 30 nhl games, 3 more are trending well and will get nhl games within the next year and 1 more that still has a shot, albeit with another team. 5 out of 7 is still outstanding work, and probably better than whichever scrub team you follow