Armor Blitz is not that bad, probably way better than Shooting Girls, and you don't need to pull UR/6 stars in order to progress, unlike some F2P titles out there... But it gets tedious like KanColle, and unless you're into micromanaging resources (it can get maddening for F2P players) and round-the-clock play to capitalize on that micromanagement, you'll probably get bored after a couple of weeks.
Nutaku's problem is that they're stuck on bringing out dated games, especially titles that no longer receive support or games that were obviously produced by amateur Flash developers (bug issues, lack of content, etc.), as well as to an audience that is anti-microtransaction (people in Asia are much more likely to shell out money for DLCs and pay-to-win transactions), as evidenced by vocal criticism online and in the media when companies out in the West provide those kinds of options, like vanity and expansion DLCs for video games (You see that all the time, like why couldn't Company A just include that in the $50 game, and that they're greedy, etc.)
I find it ironic that a small subsection of those players would be angry at Koei Tecmo for trotting out a line of DLC swimsuits for DOA5, and yet they spring for a $50 ticket to get some virtual pixel in a browser game. Sometimes you wonder how stupid humanity has become (or maybe just whiny and entitled)