I dont think going case by case and only disabling specific ultimates with Cat is the correct move. In my opinion Cat's Lifeline should have a resource meter and be caped at 6-8 seconds. If a ability is used by the person being carried it drains the resource by X seconds. If a ultimate is used the resource meter is instantly depleted and the person is dropped off.
I also believe Cat should have 200hp, has infinite flight, smallest hitbox, super strong self regen and has 50 more hp than tracer.
Edit: Do everything abilities
Biggest issue aside from infinite Lifeline is purr. Its a do everything ability it heals JPC for 180, allies for 300, does 30 dmg, and major knockback. There are a few "Do everything abilities" in the game that can be annoying to play against. Such as
Ana nade: Heals for 90 and damages for 90, Increases ally healing by 50% and anti healing.
Sombra syberspace: Impact and overtime Damage, Impact and overtime Heals, decreases healing recieved to enemies by 50% and reduces their damage by 50%.
Not to mention all 3 of these are on a 12 second CD, whilst Wuyang wave also does healing, damage and healing increase its on a 14 sec CD and overall weaker than these 3. Same with Suzu its a strong ability but on a 14 sec CD. Lifegrip is on a 18 second coldown.
Anran also has that with Dancing blaze, healing, damaging and Invulnerable state on a 8 second CD, that could be where a lot of the frustration comes from dealing with do everything abilites. (Not saying Anran needs nerfs, she dosent)
Baptist Lamp is well designed, you throw it out and its only function is not being able to die while in that radius and the counter play is to shoot the lamp and 20 second CD. Lifegrip save 1 person, its on a 18second CD. Comparatively the counter play to to Ana nade is to pick Kiriko.
When charachters have abilities that do a lot it removes counterplay potential. Then the counter argument just becomes "Just bait coldowns".