i have played minecraft since version 1.0, so around october 2011 and the game starts to get repetitive over time, and i played singleplayer exclusively for a long time, since i am very introverted. what really helped was joining my classmates' server, i am now back in love with the game and i am in love with features like the elytra and such.
Yeah playing with friends is a great way to keep your interest in the game and you can always play with the countless mods made by the amazing community. Minecraft is a game that its only limit is your own creativity.