First, both Jaxson Dart and Davin Brown played with better receivers than Isaac, IMO. Cody Hagen is better than any receiver Isaac has had, Noah Kjar > Tate Kjar, and Jett Meine is better than any WR Isaac has had outside of Tate. Both Dart and Brown had Jackson Powers-Johnson playing at center, a luxury Isaac hasn't had. So to say Isaac's offensive teammates were materially better than that of either Dart or Brown is arguable. In my opinion, Isaac did more with less than either of those guys (and I'm the biggest Jaxson Dart fan on earth. Dude is a stone cold killer).
Second, Isaac has proven himself time and time again at various camps and national seven-on-seven tournaments.
Third, the kid works like a dog. His dad has trained him from a young age to do all the extra work, both physically and mentally, to be a step (or ten) ahead of his opponents.
Look, I get the whole bratty rich kid punk thing... he exudes that aura, and always has. And while his name may have gotten his foot in the door, he's had to back up those high expectations everywhere he's been, and he's met or exceeded those expectations every time.
I don't love the kid and I don't think he was going to be a good fit for BYU, but to punish him or downgrade him because he has a famous big brother seems unfair to me. I don't hear anyone saying those same things about Tei Nacua or the younger Kaufusi brothers.