Eh…I disagree. Suiren had the first fully evolved starter since Haruka for a girl in S&M and was constantly shown to be a “girl of action” (described that way in the pre-series summaries too) She had that Ashirene because she had an affinity for sea Pokémon and it was a mascot of Gen 7…not due to it being girly. She also was at least enthusiastic about training and the league on par with Satoshi/Kaki was. She was good at sports, excelled at the ninja gym, did crazy fishing stuff and pretty “proactive” in getting down and dirty.
Mamane was more of the “insecure” character of that saga. He also had a girl Pikachu clone with a crush (because marketability). Lillie’s essentially wasn’t even a trainer in vanilla S&M until the very end and she got a cute Alolan Rokon cause it suited her with its white color and dainty appearance in her first focus episode and was dubbed as a trainer in that episode. In-general all the captures by boys and girls could be chalked up to them mirroring their game counterparts as Suiren was the only who really “broke” character with her catches.
I can understand wanting more active girls I just feel like this is a reach when Suiren was pretty proactive in working for and getting rewarded for her specialization in working with Ashirene, it’s development, the Z-Move and Ring, her master, her friendship with Kasumi, Kyogre, her lesson and resolve after losing to Guzma. YMMV, I guess but I can’t pretend all girls have been just sitting on their hands since Serena showed up and the writers have stuck to some super strict gender binary.
Remember there technically is no main girl of PM, Koharu is still just meant to be a side-character. PM is still Satoshi&Go’s story and billed that way even if she’s gotten better prominence.