It's literally nothing like Overwatch. Might as well say Overwatch is a bare bones version of Call of Duty.
Anyway, I play the game all the time on Xbone, never have trouble finding a game. I'd imagine PS4 population is higher. PC, who knows.
As for flop, would depend on 2k's expectations I guess.
I know what you're trying to say, but you're exaggurating a great deal by saying "literally nothing like". I've played both games, and you can make a much longer checklist of key features they share, compared to other games I would actually give that distinction to, such as Super Mario Bros vs Gran Turismo.
I would rather say they are a different genre of first person shooters, and trying to target a somewhat different audience. (I say somewhat, because I feel both are also trying to appeal to non FPS fans.) That said, even though I'm well aware of what separates them, to be completely honest, I too felt that it was a choice between Overwatch or Battleborne for me. And that's probably because, different genre of shooter or not, as I'm not a big enough fan of FPS these days in order to play different ones, I felt that one would be enough to satisfy my shooter fix, so to speak. On top of both games focusing on heroes with distinct charming characteristics and design, and cartoony level design, which was what drew me into trying them in the first place. I wouldn't play either of them if they were like Call of Duty with generic soldier #7 as playable characters with the realistic sceneries those games usually feature. Battleborne is trying to be more like League of Legends than Overwatch, but as I'm not a big FPS fan, that wasn't what stood out to me when I played them. It was more the combat and the heroes/levels.
I imagine some others feel the same way, and many others don't. The former may have affected sales more than Gearbox expected. You can see someone in this thread saying they thought they were the same game, and I think I mixed them up as well before I tried the Betas. For those who never tried them, Blizzard are just much bigger and better at promoting their games.
It's not an exaggeration at all. Sure, they're both shooters. You use guns in both. You can also make a very long checklist of things that are similar in Gran Turismo and Mario Kart. Are they the same? They're both racing games.
Battleborn is a character driven FPS with deep MOBA roots. You have minions, you have sentries, you have abilities and powers that unlock as you level up. Time to kill is very long compared to other FPS games. You cannot change characters once selected, so team composition is extremely important. Overwatch is a character driven arena type shooter. You have 0 MOBA elements, time to kill is extremely short. You can change your character at any time. There is no leveling up in a match, there are no powers or abilities to unlock. You have a super move that charges up like in Call of Duty.
Of course they are both FPS, that's a given. That's why my example was Overwatch and CoD, also both FPS. I never tried to make them seem as different as your example, a platformer like SMB and a racer like GT. They're both shooters, but they play nothing alike.
If you felt you had to choose between the two, that's fine. I know plenty of people who feel they have to make that same choice with CoD and Battlefield, though they also really don't play much alike in a lot of areas. And I agree 2k's marketing sucked, they also handicapped Evolve with shitty marketing.
I own both and greatly prefer Battleborn. I don't mind Team Fortress style shooters like Overwatch but it hasn't clicked with me yet.