Hiii! I can answer your question. My mom has had the same ten villagers that first moved onto her island since she started playing a year ago when the game came out. She's just only moved four out a couple weeks ago, but when she had her original, she got new recipes even after a year of playing. So, I think you are just having bad luck.
Villagers tend to change who is crafting three times a day. If you check their houses once in the morning and find a villager crafting, talk to them and get the recipe. Then come back and check in the afternoon after you did the first villager after it’s been a few hours and check for someone new crafting and get that recipe. After that, do it in the evening and get another recipe. If you do this everyday, you should find a new recipe once in awhile. At least, it’s worked for my mom.