I'm certainly not naive about pro cycling. But Armstrong, Indurain, Ulrich were 20-25 lbs bigger than Tadej. Put a 25 lb rucksack on Tadej, and see what his ascent of one climb looks like compared to these guys (well, I'm sure there's an app for it).
Pantani might be a more apt comparison. But the pirate's supplements included large amounts of Coke. Pantani was a naturally small guy (similar size to Jonas). A lot of these guys today are CRAZY lean, and surely put much more healthy fuel into their body. So, nutrition and training have improved. Equipment has improved. The "Macho" gearing has gone away.
With all that said, I'm not naive. Jonas is 128 lbs. I think of guys like Filipo Ganna in time trials. Jonas blew all those guys away by over 3 minutes in a time trial (all except Tadej, who he beat by over a minute). Sure there was some climbing in that time trial. These guys do way harder days, and steeper, longer climbs. That's the one effort I can't get my head around.
When Tadej attacks out of the saddle, he reminds me of Lemond. Powerful, athletic, gifted. Admittedly, I'm biased toward Tadej (and Remco, and Sepp). Jonas seems like an otherwise decent guy. But because of that Time Trial, and my lack of belief in what I saw, I've soured on him.