In the 1970s some vegetarians would qualify themselves as ovo-vegetarian, lacto-vegetarian, pesco-vegetarians or combinations thereof. The later had to do with not eating anything with a cute face, so apparently fish were OK.

I was a vegetarian for a couple of years (to lose weight and "for health"; neither were sustainable) and ate veggie burgers, but I made everything from scratch from real food, following Moosewood Cookbook, Indian curry and Mexican recipes, soaking beans or using a pressure cooker or slow-cooker very rarely stooping to use canned legumes. Plenty of flavour from real herbs & spices. Rather than thickeners I still use techniques like putting part of a soup or stew's vegetables in the blender and then adding them back to the pot. Big batches with extras frozen in individual servings has been my time saver for 50 years!