Realistic tactical shooters doesn't sell what they used to, it's that simple.
Well, people said the same about space combat sims and guess what, Star Citizen already received so far more than $46 Million USD and Elite Dangerous more than £1.2 Million GBP and these games weren't even released yet so were those same people right? Obviously a HUGE and ROUND NO!
And I'm sure that if there was a good tactical shooter that it would also be a great success. The problem is IMO mainly because of two reasons:
1- There isn't any MODERN and GOOD tactical games nowadays! The latest and most modern tactical game that was released was that crap called Takedown:Red Sabre. Most (realistic game) devs seem to believe that since there isn't many realistic games nowadays that if they release one even in an unfinished and crappy state that people will jump in and purchase it - Well they couldn't be more wrong - Most people won't buy crappy games being it realistic or arcadish, period!
2- Most game companies seem to be run by suits that hardly know what a PC game is. They look into charts and "Excel spreadsheets" and the only thing they see is that arcade games take less time and money to develop with possibly more customers and thus a possibly bigger profit! And this is all that companies seem to care about nowadays, making the most profitable product possible without caring about quality and are not interested in making something that they could be known and renown about (as opposed to 15 years or more ago).
And BTW, if tactical shooters weren't profitable even nowadays, why do game developers such as UbiSoft use the name/brand of well known and realistic tactical shooters for their games?? If this was the truth (tactical shooters don't have any chance of profits nowadays) I'm sure that UbiSoft wouldn't have the need to use the Rainbow 6 brand and would invent other name.
And I, my opinion, don't have the stamina for realistic shooters anymore. In the early 2000s I could have sunk my teeth into the ARMA games and the planning stages of the original Rainbow Six games, but now I couldn't care less. So Siege, BF and so forth are the norm. I'm looking forward to Siege, and had a lot of fun with the two Rainbow Six Vegas games.
Well in my end, I have less and less time to play games nowadays so when I have the rather rare opportunity to play games, I want to make every second count and I want to spend it playing GOOD (and realistic) games so I won't waste a single second playing arcadish crap.