The devs on Apex said that Solo wasn't healthily for the game, and that everything from some legends being useless, to the map, to the loot was designed with a team of 3 in mind. However, the thing about that observation is that the map isn't even a problem most of the time. Loot is scarce anyways. While each legend is useful in their own way.
Bloodhound: The legend will be able to fully embrace the tracking abilities to find enemy players and kill them all to win.
Gibraltar: While he's unable to be much on the offense, he can still protect himself and make handling other players easier.
Lifeline: A healer and can call in a care package. She's not useless at all.
Pathfinder: He will be able to keep finding the next ring location, as well as be able to move to well positioned areas.
Wraith: While she can phase, people think the portal would be useless. Not at all... actually... You could use the portal to cause enemy players to run into thermite, or off the map. Or just use it to get into the zone.
Bangalore: She would be able to smoke out her enemies and get the drop on them... like the solider she is.
Caustic: While people would camp most of the time, he would be able to hold positions and gas out enemies.
Mirage: He was sorta useless during the Iron Crown event, however he can control decoys now, so he can actually trick legends, as if he's a two player squad.
Octane: His abilities may seem useless, but being able to naturally heal and run makes him best to chase down fleeing enemies.
Wattson: Like caustic, players tend to camp as her, however the ring keeps moving, so they must keep moving. Besides Crypto can just break her defenses, and Loba can just teleport into the room. Her interceptor would help in battles.
Crypto: While the drone is pointless most of the time, it would help with seeing if anyone is close, as well as disrupt them. I believe Crypto can be decent as a solo. He was on of the ones picked during the Halloween event, due to being able to leave a drone to scan the evac ship for hostiles.
Revenant: He's already proven to be on the offensive. Silencing players and entering the shadows. There's no reason not to use him.
Loba: She is not at all useless. Using her would allow players to quickly get what they need to win.
I can admit that using characters like Octane can be seen as "useless", but they're only useless if the player is unable to use their abilities to their advantage. I don't see how solo isn't healthy for the game. Each legend competes for their own reasons and the fame and glory shouldn't have to be shared. The only two issues presented with solos, was that multiple players would use the same legend. Causing a game full of Wraiths and Pathfinders. I don't think that was even a real problem. Due to Pathfinder's debuff, I doubt many people would pick him, while Wraith has been constantly debuffed because players refused to get good and find ways to counter her. Most of the "debuffs" the legends get is because someone doesn't have the proper skills to kill the legend. The other issue was players would team up. I've seen games where two Pathfinders acted like a team. An easy counter to that would be adding a "report teaming" option, and make the game flat out give both players who are teaming, a timer to kill each other, or the game kills them instead. The thing about teaming as well, is that it isn't even solos. I've played a match back in Season 1, where four full squads were playing as a team. That's right 12 players were playing on the same team. I haven't seen teaming like that in a while, but I still see two teams teaming from time to time.
The thing about solos, is that many players can survive on their own. Many players rather to depend on themselves than some random ruining the match because they're new, refuse to listen, disconnects, complains, etc. What negative impacts has solo brought to Apex besides multiple players being the same legend, and players teaming? Because there's so many bugs and nonsense, that the map and ammo part of "why solo isn't being added" is thrown out the window. I mean yes, players camp and wait until there's one person left, and then kill them. However, that happens in Duos and Trios anyways. Solos could also work if the ring started out slightly smaller, and closes quicker. Players could even drop in with armor and a weapon, like we've seen in a recent event.