The novel is: Why Is the Prettiest Girl in School Trying to Talk to a Loner Like Me during Lunch Break? https://www.novelupdates.com/?s=Why...+Me+during+Lunch+Break?&post_type=seriesplans Any information is appreciated.
Well, there are many of somewhat similar concepts (there are many): Oretachi ni Tsubasa wa Nai Gamers Anime Nyan Koi! Nogizaka Haruka no Himitsu Amagami SS
I think Gamers is probably the closest in concept because that's the only anime where he's both a "Loner" and she's the "Prettiest Girl in School". In the other anime you listed the dude isn't a loner, in fact they have a straight-up harem in some of these anime. Not that they're bad or anything. In fact, they're all great anime. Amagami SS is peak rom-com, nothing can top that.
I don't read that novel, but from the description the closest one I could think of was probably Oregairu
Too plain, to become anime, must have a meme potential is what they're looking in bland tropes like idols, old trope but add zombies, idol zombies = zombie land = profit, racing, old trope add horse girls = uma musume = profit