Maokai can only ulti for 12 seconds preventing him to abuse mana

A champion has a single characteristic in one of their abilities disregarding whatever else it does.

Meanwhile other champion that has other abilities, functions, and roles in a team composition.

swain's ult is his main source of teamfight damage. His Q is mediocre at best, its main purpose is CC with a little damage thrown in. His main CC is his W as it roots in a ground aoe. E is a source of damage and debuff that boosts his overall damage on a single target. His ult is his main source of damage and sustain, it's what makes swain himself and his gameplay, a sustain mage and it has to be a toggle to control his mana usage.

Maokai is pretty much a full-on tank with a few exceptions where sometimes you can build him AP, like ARAM where those saplings hurrrrrrrrrrrrrrt. One of the reasons maokai can get away with being a tank and do damage is because his W does % max hp in magic damage, he has good cc, and passive healing that heals him for a % of his own max hp. Q has a decent amount of cc and a knockback. fairly low cd at later levels, can interrupt some abilities. W lets him dash to a target, roots them briefly and does % max hp magic damage, meaning this is still decently effective against tanks. E is a long range ground cast "mine/bomb" that targets a nearby target, priority champions, and has a slow. decent for zoning and slowing potential fleeing targets, pretty long cooldown and high mana cost early to prevent abuse. now his ult, which was the main issue. his ult, If I haven't forgotten any patches since I don't play maokai often, also grants the damage reduction effects to teammates in the aoe area, meaning he's also providing utility to his team with his ult and can negate a good chunk of damage with it which is why they gave it a timed limit since a maokai can just pop it on and initiate a dive while tanking tons of damage, plus his passive charges with any and all abilities acst within a range of him to heal him for... what was it 7% his max hp, so the more hp/tankiness he has, the better. maokai also has more CC then swain.

The two champs are also different roles and swain doesn't really do anything if you build him tanky like maokai since swain HAS to do damage to heal and has no gap-closers or ways to initiate other than perhaps landing an aoe ground-cast root as opposed to maokai's targeted root-dash. While liandrys could potentially allow swain to do damage while being tanky, it would require him to potentially be in ult for a long period of time to let the damage keep rolling, but then again if he's going tanky his role isn't really to do damage as much as it would be to interrupt the enemy team and make potential picks and get out alive, something he cannot do as well as mao can due to his kit.

tl;dr different roles, different kits, different purposes for both so not really a good idea to compare them just because they both have this duration-type ult mechanic as they're both meant to do different things.

This would probably be a more valid and highly upvoted thread if Maokai weren't also broken.

Swain's ult duration is soft capped because the mana cost increases over time.

Maokai has a dash. Meanwhile .