I wouldn't say they're selling poorly, per se. There's definitely figures that hang around, but it's totally character/project dependent. Vernestra and Bazil have stuck around my area, as well as the evergreen Vader (I totally get the point of the evergreen figures, but I still do worry that they either skew either our or the retailer's definition of what's actually selling). Some Targets I've been to have only a couple Vaders out at a time and replenish as need be, and some just seem to put the whole shipper out at once- they're stupid with Vaders, and they just hang around for months and months. Ironically, I think the evergreen figure that would work best would be a trooper- Storm or Clone. Especially whenever there's a slight sale, I can totally see nerds going "why not?" and grabbing another army builder to customize or throw on the shelf.
The other figures that have hung around here seem to be from the Disney+ projects that didn't do too well- Acolyte and Skeleton Crew. Both of which I love- the latter of which, I think a lot of fans would love too if they'd just give it a chance and not take themselves so seriously. Enough to get figures of? Arguable, but still.
Not always, of course, but saber wielders tend to sell pretty darn well- hence every single Clones of the Republic pack selling out pretty quickly. As do Mandalorians, cool aliens, and Maul himself, so by that metric, this Maul wave is a slam dunk for a lot of people. New projects almost always tend to raise interest in a line, and since the next 2 are tried-and-true (character-wise, at least), I think we'll see an inevitable resurgence of interest.