A few things:

• What wisp does for herself she also does for the group. Your teammate can afford to bring a frame that’s not survivable enough normally because of vitality mote, and with very little coordination from the group.
• Because of the way reservoirs work, that strength requirement isn’t as much of a tradeoff as it seems. Wisp can afford to tank her efficiency into the ground and still function very very well in any mission where you can stay near your reservoirs.
• You compare her to arcanes, but those are a very large farming investment to get to high levels, whereas she drops from a boss fight / relics. If you’re one of the players that already has everything the comparison is fair, but if you’re looking at a new thing to acquire the two are very different hurdles.

Ultimately she’s probably rarely the best possible choice, but part of the reason that she’s considered “the best support in the game” is that she does so much with so little investment or effort (and that she was given that title before a bunch of older support frames got buffed to stand on par with her)

Does this count? I’ve got a +multishot +fire rate -(100%)damage tetra riven I use with mirage to terrorize my friends while contributing nothing to the mission