I feel like these guys are comparable if you narrow them down. The Ponder/ Rosen type of QB is a smart and intelligent guy who probably doesn't have much room to grown further as a passer. But you know what you're getting on draft day with this type of qb.
My Gabbert/Darnold comp is probably because I'm not high on Darnold. They both got the size and right tools. But they still need to grow as a NFL QB. Gabbert was mobile and knew how to make play out of the pocket. The anti-Newton fraction had him as QB1.
Kap and Jackson are both very athletic guys, but there were/are questions how their play will translate to the NFL level. But we all know if they're figuring it out it ends up being lethal.
that rosen/ponder comparison still doesnt jive - rosen is already a better qb than ponder was and absolutely has room to grow - remember that he was working with nothing at receiver and swiss cheese for an offensive line and still passed with anticipation and was the most effective passer down field of all the qbs in this class despite allen and darnold having the flashy cannon arm talent - rosen is absolutely the most pro-ready but that doesnt mean he has a low ceiling as a prospect - on the contrary i think his intelligence and evidence of anticipation and nuanced understanding of defences and the playbook suggest his ceiling is incredibly high and as long as his body holds he's more likely to reach it than the other guys
im not darnold's number 1 fan but he's still miles ahead of gabbert - the only similarity is that they are both sneaky very athletic - but darnold has a cannon and takes risks and is dynamic throwing the ball down field - gabbert literally had the gabbert-zone named after him (when a qb averages 5 ypa or less)
kap and jackson arent really similar either - jackson's a better athlete and better at keeping his eyes downfield and scrambling to pass rather than run - kaep had a cannon and you could argue that jackson hasnt shown a huge amount of touch (albeit he's started presenting touch passes to scouts etc through this offseason as well as working from under center so you know he already knows and is working on improving those aspects) there's also a much higher accuracy upside with jackson if you can sort his mechanics whereas kaep just had a 1 dimensional stare-down cannon but was only effective in RPO whereas jackson seems scheme diverse to me
the other thing to remember is that in 2011 teams were trying to manufacture round 1 qbs by elevating day 2/3 guys with elite traits and selling themselves on the idea that they were round 1 talents and they got burned
in 2018 some teams might be hoping to elevate these qbs but they are projecting forwards with guys who already have the talent - theres a difference between raising someone 2-3 rounds in the draft (like gabbert who had 4th round grades from a lot of scouts and organisations at the time) and raising someone maximum 10 spots (darnold may go number 1 but would but would be a top 20 player on virtually every nfl board and likely top 5-10)
there's really no comparison between the classes at all - and any comparison really is disingenuous