I feel like the main reason this is true is because of the questionable selection of cross-class skills. There isn't an especially large variety right now, and some of the cross-class skills make me wonder why they were made cross-class to begin with.

Maybe if every ability up to half of the maximum level (so, Lv25 for now) was cross-class, Jobless characters would become more viable. Or maybe make it like FFV, where if you maxed a Job, it would confer some benefits (e.g., bonus stats, and maybe one Job Ability and Trait) to one or more Classes.