Videos like this REALLY make me curious how Pokemon type analysts would see the addition of the Love type.
Just sticking to the type chart I made...
Well, for starters, the type obviously nerfs Steel. It's a defensive powerhouse that dominates the meta, with only a lucky few types able to hit it for big damage while also being able to dominate the offensively mighty Fairy type. Love stops Steel in its tracks - after all, love is said to be stronger than steel. Yet Dark might actually get it worse - without the defensive dominance Steel has, Dark would probably plummet on the tier lists as teams start picking up Love types to deal with the metal walls on everyone's teams.
In particular Bisharp and Kingambit are hurt BAAAAAD by this. Not only are they quad weak to Love, but their STAB is COMPLETELY walled out. Other major victims would be big meta threats like Weavile, Chien-Pao, Tyranitar and countless, COUNTLESS steel-types that aren't paired with the Bug-type, or Metagross.
But talking of bug-types, there's also a good amount of Pokemon that would greatly appreciate the Love type's addition. Poison already got a huge win when Fairy was added and this will just add to their viability. The Bug-Poison types in particular would be thrilled, as they'd have a mighty quad-resistance and huge STAB potential on a likely dominant type.
But of course the big winner is Psychic. Before now Psychic was dealt a pretty crummy hand following its dominance in gen I, with nerfs hitting it full force in gen II and generally falling off due to its lack of real offensive properties. So naturally, if they happen to get a type that they not only can hit for big damage but are also IMMUNE to...yeah, big boon for the Psy bois. Alakazam could see a return to prominence, Metagross would essentially become the new best Steel type in the game since Psychic covers for Steel's usual Love weakness, Orbeetle and the Galarian Slows could become big competitive counterpicks, among other buffs.
That's just a little of what I think could change if Love type became a thing.