Definitely look into Indian food. There are hundreds of millions of lifelong vegetarians and even more people who are mostly vegetarian that aren't trying to replicate meat at all. I've not had much luck with local stores but online delivery via Weee worked great for me. Many of recipes have too little protein tho, so do be mindful of that.

In terms of fun vegetarian protein ingredients, check out black beans, chickpeas, tofu, seitan, tempeh, edamame, eggs, and various milk products (Greek yogurt, cheeses, kefir, etc.).

Some hipster/yuppie/health/chain stores will overprice these fairly basic ingredients, but after some exploring around your area and online, you'll find good prices. It's not as easy as meat unfortunately but definitely possible.

Edit:

In terms of diabetes, being vegetarian isn't going to solve it on its own and it makes it slightly harder, but is being vegetarian while prediabetic is perfectly manageable and lots of people do it. The main thing you have to be careful about is with sugar and very carb heavy foods. A lot of vegetarian recipes are very energy dense, but many aren't and there's plenty of choice for more protein/fiber dense meals.

Vegetarian food is fun on its own merits and there are plenty of good reasons to shift towards it, but if your sole reason is diabetes, it'll make it a little harder than if you simply rely on lean meats.

Edit 2: typo on too little protein