Here's the thing, you absolutely can sell music like Siren Charms and Battles in the US. Plenty of equally shitty bands do it. The issue is that In Flames are now way too old to pull off the image needed. You need guys in their early 20s with make up and techwave/postpunk futuristic fancy image. Not 50 year old middle aged men who are balding, especially when they can't even pull off what I guess should constitute as singing live.
In Flames want to tap into that Black Veil Brides market, and it makes sense given how there is a lot of money to be made off western high school girls. It's just that this band can't pull it off - neither in terms of looks nor in terms of absolutely driven social media campaign that is necessary for such thing. You need youthful energy for making it in the modern music business.
If the band ended up quitting within the next two years, I wouldn't be the least bit surprised.
Siren Charms is a weird album, it doesn't really have an indentity. It runs through average/poor alt-metal, rock ballads and electro-pop. I am not sure it was aimed at anyone in particular - a jack of all trades and master of none. I'm not really sure who it was meant to appeal to. Battles I would agree is a stab at a younger US market - probably the most calculated album in terms of aiming at a demographic since STYE which was a very obvious attempt at penetrating the American alt-metal market.
As for how long IF can go on for, I have no idea. I can't imagine Anders and Bjorn still doing this stuff, with touring and everything else, into their mid-50s. I would guess the band have a couple of albums left in them but I would be surprised if they are going much longer than 5 or 6 years. In terms of output IF are surely up there with some of the most consistent bands of all time. They've released regular new albums every 2-3 years since 1994 which is impressive regardless of how you view their progression. No hiatus or break up during that time, just regular albums and tours. Many of the bands from that early-90s Swedish MDM scene (DT, Soilwork, Arch Enemy) have been amazingly consistent in this sense, which is impressive.
I had no idea Lunar Strain had such a bad rep before I got online. I think it's pretty awesome and I prefer it to anything after Clayman. I think there's some amazing stuff on there like Harlagaten.
When I first started discussing IF online in the early 2000s Lunar Strain did not have a bad rep. Most people liked it and there were quite a few who even preferred it to the likes of Colony and Clayman. It's only really been in the last 10-12 years that LS has started gaining a bad rep amongst IF fans. If I had to hazard a guess as to why I would suggest it is because fans 15-20 years ago had mostly come from a background of listening to 90s MDM/DM/BM. The current IF fanbase doesn't have that foundation, for a lot of them their first IF albums were STYE, Come Clarity or ASOP. So the appreciation for that older style of MDM/DM isn't there and so they don't really understand LS and cant get past the production. In the 90s it was normal to hear that kind of production on extreme metal albums so you just got used to it. I guess it's not so easy for the current generation of IF fans to accept that.
Basically, those of us who listened to that old style of MDM/DM/BM and also still listen to IF are a minority as most of those fans abandoned IF around the Reroute/STYE era and have been dwindling ever since. Lunar Strain is not a bad album for those of us who grew up lisening to that kind of metal, but we are a dying breed as far as IF fans ae concerned - it's the sound of our playground fading.