I suppose it depends on how you want to measure a lineup. Sure, Subaru's products now lean heavily American, but even with fewer options, they've managed to grow their sales all while increasing their reliability/quality scores and improving their resale value numbers. That's tough to do in a market that's as competitive as it is in the US. But, we've also got to remember that Subaru was basically on their own for, what, 30 years, doing the AWD sedan thing? Sure, Audi was in the mix too, but aside from them, it was only "specialty" models from Mazda, Ford, or GM that offered that kind of setup in the US. These days, everyone's got an AWD sedan to offer - proving Subaru's point from the outset.
One thing I'd also consider would be the mountain that Subaru has been able to get over that some of their competition has not - that's repeat buying. Its pretty well known in the US that the average Subaru buyer is very similar to that of VW, Volvo, and (formerly) Saab... Three companies that have struggled to maintain their market share due to poor product planning and too much of a recursive buying structure that didn't bring in new customers. In the US, VW's product strategy is a disaster, and while Volvo's is improving, you sometimes have to wonder how many of their buyers are Saab refuges. Subaru got past the hump by bringing in younger buyers (the WRX is great advertising), mainstream shoppers (Legacy is as reasonable a choice as a Camry now), and the booming crossover buyer (the Forester is still class-leading in some respects). Their lineup is boring, absolutely, but that's what the people who are buying want... But, there is enough of that Subaru soul there to keep their traditional shoppers happy, and many of their products are just quirky enough to bring in curious people, and get them hooked on what has been bringing people in for 30 plus years.
Mazda in the US is an entirely different story. Without the Ford support, they have to be much more careful with product development and execution, and thus far, they've proven to be great at making exceptional cars on a budget. But, when it comes to actual innovation, I definitely feel like Mazda is more or less preaching to the choir - as in, doing what the enthusiasts want, but in a mainstream fashion - that gives the false impression that they are completely class-leading in any shape or form. Clever engineering is clever engineering, and they're arguably the best at it given their smaller pool of development funds. But it isn't like they're reshaping the idea of what needs to be done. Their products are successful because Mazda people want more Mazdas, and they won't shut up about it, and they get people like me who like what the company is doing, to also not shut up about it. In a weird way, Mazda today is pretty much like what Subaru was 20 years ago, doing their own thing and being reasonably successful, but that doesn't make them some kind of special force in the industry.