Not to trash this stallion at all, because I like him (and one of the "stallion candidates I mentioned was sired by him), but let's look at Ideal. He remains either #1 or #2 for siring the most Premium foals for ISR/OldNA in their history! I think he might still hold the record for highest scoring foal for movement.
And he sired 100's and 100's of foals during his breeding life. So where are all the top performing Ideal offspring in either dressage or eventing or jumping? Yeah, there are some, but not near the number that one would have thought given the huge number of Premium foals he produced.
You are forgetting the fact that he was known for passing on a sane, trainable attitude and the VAST majority of his offspring went to amateur homes- where the owner has no intention of ever aiming for the upper levels. The few that sold to top competitive homes, typically were/are very successful.
And after all these years in breeding I do believe that you can "judge" a lot of things quite reliably (not 100% though) from looking at 4 to 5 month old foals. The good ones usually turn into good adults, and it certainly makes a difference to educated buyers.
Worthless, no! That said, mistakes are occassionally made. Usually the Top 10 foals go on to become stupendous horses,
Again, Ideal sired many, many, MANY Top 10 foals (and again, I'm just using him because I bred to him), but most of them did not go on to be "stupendous" horses, unless you are using the term to describe very nice ammie horses.
One of the colts I bred by Ideal was graded #2 at his inspection and deemed a stallion candidate. He is now 10-12 yrs old, still with the woman I sold him to and has done ok in the H/J world....but stupendous? I don't think either myself or his owner would use that word....