Sorry for the late reply…
Grains are pretty high in protein content. However, oils (e.g. fried foods), sweets and fruits and often pretty low in protein. If you are eating a “what ever I crave” vegan diet with processed foods mixed in, you will easily land below that threshold.
For example, my wife tracks her food sometimes (for a couple weeks each) and she often lands below her recommended target. She is not eating badly but also not suuuper clean and still, she often does not reach her recommended protein amount.
Bottom line is: You can easily be eating “not enough” protein. However, most of the time it will not lead to big problems. But in the long run, this might get problematic. Every person - vegan or not - has to plan their diets well and think about what they eat at least a little. “Being vegan” is not a magic wand of nutrition. We still need to consider what we eat every day.
You could look into using 3rd party clients to view Lemmy. They often enhance the default behavior with additional features. E.g. Voyager (the one I’m using) has a “keyword filter”.