I don't think this is empirically true at all. It is very easy to see failure within your own team, but I think you would be shocked if you looked at the draft history of some of the teams around the league who are presented as "good" in the draft. The Jays by and large have been drafting at the back end of the order year over year, and they also generally don't receive extra picks; despite that they have found elite prospects (you need to appreciate how unlikely it is to find a Tiedemann level talent in the 3rd round) and have generally found guys that are still performing with later picks (eg: Connor Cooke was a 10th round selection and he has an absurd 55 K's in 29.1 IP this season). It's really easy to wash away Nick Frasso as a 4th round pick, but that is a major hit by actual empirical odds.
Most picks by and large are going to fail, and this isn't something only reflective of the Jays. It's just easier to see when it's your own team. The Rays for example receive a million extra picks every year, and their flop rate is disgusting. And this is a "model team" that you would assume is just nailing it every year. For example, from 2018 to 2020 their top picks were Brendan McKay, Matthew Liberatore, Greg Jones, and Nick Bitsko. That is 3 complete busts (McKay, Jones, Bitsko were/are horrible) and Liberatore has made the MLB, but he's been utterly horrible. So that's 4 straight years of absolutely nothing, with McKay being a Top 5 pick. Nate Pearson is a success in comparison to those names. It's easy to see Austin Martin and say WTF were they thinking, but look around at the other top picks from 2020: Torkelson has been bad, Kjerstad looks good, Max Meyer bad, Asa Lacy atrocious, Emerson Hancock bad this season while repeating AA, Nick Gonzalez might be something, Robert Hassell is flopping, Zac Veen is horrible, and Detmers has been a success.
The Jays record of top prospects flaming out at the MLB level is also not in any way unique to them. The final jump to the MLB is a massive one and this chews up elite prospects every year. I don't think it's indicative of anything to point out that that the prospects they've traded have largely failed for the teams that acquired them. Has CJ Abrams been a big success for the Nationals?