Joe is very much a nostalgia property. Every time they try something new, it either reverts back to ARAH or if moves away from ARAH it dies. GI Joe 25th is a perfect example of this. It went from two single box sets to absolutely DOMINATING to the toy aisles for a few years, they moved away from ARAH and it quickly died off. Classified started as sort of a "modern take on Joe in 6 inch" with more military and sci-fi mixed in, but not necessarily classic designs. It did okay but stumbled a bit. As soon as they switched to straight up ARAH, it took off.
You can pepper in SOME new stuff of course, but ARAH is what keeps it afloat. There are also big AT and even Super Joe fandoms out there as well. But there's nothing "new" with Joe that's connected with people in decades.
I think the Joe MMs weren't as successful because a lot of issues with rollout and it was the same ol' stuff we usually see as the launch for Joe. The GI Joe Megos failed because they launched with SS and SE, which IMO is a mistake even though they are arguably the most popular Joe characters, Mego collectors didn't want those figures first. You're not going to get Joe fans to jump into a new format just cause of SS and SE, they have 800 versions of those guys. A new version of them doesn't excite them. From a business perspective it makes sense on the surface, but two seconds of digging under the hood you can see why it's a mistake.
MMs issue was not so much character selection, though that was an issue, as it was not playing to the format's strengths. What was the #1 thing everyone here asked for? Army builders. That would have appealed to MM collectors and Joe collectors as opposed to another SS and CC. But that's been beat to death.