No, alola is not pitiful because it is new, it is pitiful because almost all the peoples who entered in are not even regular trainer.
Illma, someone who was good enough to enter the Kalos League like Ash and the others in XY did, was brutally torn to shreds by Guzma immediately after the battle Royale portion was finished to weed out the nobodies. This is nowhere near "pitiful".
Out of the 151 competitors, only 5 including Ash, can really be called trainer, all other peoples are not even worthy of the trainers kicked out of the other regionial leagues at their first prelim battle
See above. And if you want to play that game, we can do the exact same thing for the other leagues too who were more or less than the same thing.
Every league had only a handful of people, including Ash, that were considered the actual competition from a narrative and scaling standpoint. The COTD fodder that filled up the ranks were there solely for slot filling and not anything else, minus the plot devices that the writers would shoehorn in to stop Ash from winning the previous leagues. Hell, the Kalos League literally only had Alain and Sawyer as notable competition, and
skipped the non-character matches entirely. 2 people were the only ones seen as any notable threats in that whole league going by this logic.
And if going by that, Alola's most definitely not at the bottom of the totem pole.
Does a league with peoples like james, lana and sophocle ranked in the top8 can be called prestigious? trainers like mandi, nobody guy beaten by gary in ice field or gilbert from hoenn prelim are ten times more skilled than half of manalo top8
Again, see above. And like others said, trying to cross-compare different regions and their trainers skills is just stupid entirely. Regions do different things from each other all the time.
And once again, Alola is a NEW league. You cannot expect its competition to literally be as "prestigious" as the other leagues, who have done their competitions for generations. You'd appear more credible if you compared Alola to things like the battle frontier (which wouldn't really help you since both competitions involved Ash battling and defeating legendaries, which sets the bar for him accomplishment wise).