WP Fortress doesn’t seem spectacular to me, WP technically synergizes with his ult significantly but you can’t afford to only play around only that. Going WP you try to compete with peeps like Glaive and other bruisers - Fortress isn’t a great solo diver and his CP Path is good in part because its bursty on-hit stuff. It doesnt have to maintain contact with the enemy to deal good damage. So I would say WP Fortress isn’t impossible to make work, its just… suboptimal and overshadowed by more reliably WP carries imho.
CP Cath is a bit different. Catherine as a whole is a disruptor, rather than a full out defensive or offensive roamer. As such, her ability to protect and initiate is rather lacking, even invcluding some lucky ults. CP Cath would be ok as a utility carry that focuses on protecting a more important one such as Baron or Skaarf, from enemy interference. You would not use CP Cath in place of an actual roamer in 5v5. Keep in mind that its literally only useful for her A and C coming off of cooldown faster. Her damage is suboptimal at best, and she will be squishy. Some will make the argument for stacks, but that’s… just not going to happen, and is a different discussion. I mean come on, risking your life (or your teammate’s) for 1 armor/shield???
I can imagine CP Cath working in part of a chain CC comp, or as a splitpusher with Stormcrown maybe, but not much more. She just doesn’t have the damage to be an actual carry, which is why CP Catherine spams cooldown and items with on hit effects.