Using MLBpipeline rankings(I'm not a fan, but for this general use they're fine) since 2014 through 2018 of Cleveland's top 10 prospects(not even top 100) I'll give you how many of that 10 have/had MLB careers.
2014- 8 of 10
2015- 8 of 10
2016- 8 of 10
2017- 7 of 10
2018- 8 of 10
I didn't bother counting every year of the top 100 prospects but I glanced at a few years and a large portion of those prospects are currently in MLB. The "failure" rate is not 70%, not even close.
Getting to MLB and actually producing at that level are two different things.
Do you really count Zimmer, Frazier, Chang as successes?
I'm gonna use Fangraphs, because its easier for me to access...and I'm not counting anyone twice.
2014
Lindor....success
Frazier....bust
Cody Anderson...1.3 fWAR in three seasons.
Bauer...success
JRam...success
Naquin.....4.8 fWAR in six seasons
Wolters....1.7 fWAR in six seasons
Mejia....1.3 fWAR in five seasons
Paulino....bust
Rodriguez...bust
2015
Ramsey....bust
Sheffield.....1.5 fWAR in 4 years
Mitch Brown...bust
Urshela...1.6 fWAR in 6 years
2016
Zimmer...2.6 fWAR in five years
TMac....TBD...1.7 fWAR in two years
G Allen...bust
Bradley....-0.1 fWAR in two years
Benson...R5 eligible
Jones ....?
EGonz....bust
Chang....0.2 fWAR in three years
Aiken...bust
2017
Yandy....4.9 fWAR in five years
Holmes....bust
2018
Bieber...success
Haase...0.5 fWAR in three years
Castro....0.9 fWAR in three years
Thats 28 prospects.
Four successes so far...
Lindor
JRam
Bauer
Bieber
Too early to tell...
TMac
Jones
But if your expectation that any of our present top 10 are gonna step right in and produce, the other 26 have been failures. The best of the bunch has been Yandy, who has averaged 0.9 fWAR over 5 years.
In the BA evaluation I referenced, they set 1.5 WAR per season over six years as the breaking point between success and failure.
So ask yourself this...
If Arias comes up and puts up 4.9 WAR over the next five years, is he a success for us?
Not in my book.
Not counting TMac and Jones, the success rate of our top ten prospects 2014-2018 (5 years) has been 15%...four out of 26.
If you count Naquin and Yandy as successes, the rate is 23%