It was a failure at launch no question about it. We're way past that now though. If we're to compare it at it's current state I dont know if I would call it a failure but relative to other Battlefield games it's very underwhelming. I still have 500 or so hours in it which is way more than any non-Battlefield Game.
For me its disappointing for many reasons the top of which is horrible maps. Most maps aren't really fps maps, they're more like sections of open world games. They're not designed to work in an fps game.
When there's almost no buildings or other assets in a map the only thing map designers can do is to play around with the topography. Cover based on topography is horrible because it's hard to tell if you're actually in cover.
Compare maps like Mercury, panzerstorm, Hamada, twisted steel, Narvik, Fjell to histrocial epicness like Grand Bazaar, Karkand, Caspain Border, Oman, Outbreak, Noshahr canals, Operation Locker, Amiens, Fort de Vaux, Achi Baba, Nansha Strike, Propaganda, Pearl Market, Silk Road, etc... and you're left very underwhelmed.
I pretty much just play 5 maps over and over in BFV.