This is a tough question for this board, because everyone here is presumably biased. Traditionally, furry characters are a minority in games to the point that nobody even wonders the fatal question "did a furry make this game?" Think Breath of Fire, Wing Commander, Shining Force, or the early CRPGs with furry races. That, I think, is key to not turning away normal people who have an idea what a furry is. When it's obvious that the bulk of the characters in a game's world are anthro, the questions regular people immediately ask are: "why are there furries in this game," "how is this game different or better with furries in it," and, for slightly less regular people, "are people beating off to this game's characters right now?" I think you have to convince people that you're not making a game just to have X With Anthros--unless maybe you come out an admit that, yeah, it's X With Anthros and try to shrug or laugh it off. For games that aren't porn, it's probably simplest to do it by making it clear that there are plenty of humans in your game's universe, but you just happen not to be telling their story right now (Undertale I guess, Cave Story). If anyone can accuse any of your characters of being anyone's fursona, your game will tank, so try to make the character designs err on the unspectacular side. Lugaru and Overgrowth did this well, I think, but they still plunked, so I'd call this one necessary but not sufficient. However, this should be straightforward to do with a mudslog WWI-alike as long as it's not too stylized. You could consider making one important faction consist of animal ear people to tone down the furry quotient. Naturally, though, the best alternative is to be Japanese, because they can get away with anything (Star Fox, Solatorobo).
Evidence is pretty weak, I think, that regular people are coming around. CNN, I remember, ran last year or so an outright flatter piece on furries, but even it was just a conventions-and-fursuits-apologist thing. Even with the expanded market for gaming in recent years, most gamers who'd play an indie game are probably of the crowd that'd be turned off by anthro characters. I believe that Undertale was a fluke and helped by the fact that the PC is human, even though most games that were furry-with-human-PC would be laughed at for being that isekai wish fulfillment thing.