There’s actually a really lazy vegetarian meal I like that leans hard on mushrooms. You pretty much steam equal parts broccoli and onions then add the same amount of mushrooms for a slight bit more steaming, then mix cream cheese through it, then that’s your base for a cottage pie (meaning you put buttery mashed potato on top and bake it). It sounds awful but it’s really good.SO YEAH.
Lifelong vegetarian. Find a few vegetables you really like, and use them in place of meat in your dishes. This makes ordinary dinners possible. Spaghetti? Grated portabella in the sauce is awesome. Steamed broccoli can be too, it depends on your palate, you'll want to fuck around a lot like a scientist. There are so many mushrooms out there, a wide variety of textures and flavors. Cauliflower steaks, mushroom burgers, almonds, cashews, legumes.
Figure out what you like and add it to the meals you are accustomed to enjoying.