First of all, fantastic work on this skin
I still have to try out this new attribute-less trend, but I would imagine it could be similar to how real life works, so to speak.
IMO, it's better to initially test it out with the team you support and watch on a weekly basis, so you don't need attributes and whatnot to know how good/bad they are (well, in RL at least; I know players often perform differently in FM), and maybe replicate the tactic they usually play with, at least on a basic level.
But then, if you REALLY want a realistic approach with everything else, it's just a matter of watching your next opponent highlights of their previous matches, just like analysts and 1st team managers do in RL. Same thing with potential purchases: you watch them play in their current team to assess them, just like a scout would do (and also check their traits, yes). Now, that leaves out training and the related attribute increases, so I'm not sure how that would work for the training min-maxers out there (but I guess you can still visualize trait development)
Yep, VERY time consuming (so might not be everyone's cup of tea, especially if you like to use the "instant result button" and also breeze through seasons), but kinda rewarding; it might have potential, at least with a portion of the player base.