Same boat here, I really loved Spencer's route. It's the first I played, and after finishing Harold and Chester's route, Spencer's still my absolute favorite. He's really just the best boy and all his lines are my kind of sap. He's amazing, and replaying his route over and over never gets tiring for me. I love him way too much to ever get tired. In this world, or the next, longer and brighter than any star in the universe, he'll always be the best~!
(minor spoilers) If it's any consolation for you to try out the other routes, for Harold and Chester's, Spencer still has that "I love you so much, but I'm too shy / scared" vibe going on between you two. He's always so supportive and loving, it makes playing the other routes worth it just to see how Spencer reacts. Even playing a doubles match with you, it's the only time you see his happier face sprite that entire route. He's best boy no matter what route! <3
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I don't know how to properly spoiler but I'll try.
(Spoiler)
And Chester's and Harold's routes are far less overt about Spencer's feelings than Dozer's and Darius', where it far more pronounced in both, especially Darius', which makes sense considering he's the only one that had ample time to fall for MC as proven in his route.