Yes it is time to complain. I have been doing it for a long time. If memory serves right, on LHR brunch flights the vegetarian option was the infamous tomato and mozzarella salad. In fact, I have seen this as rest of the day meal.
Whenever I complained, the answer was copy/paste and I don‘t think that it is being taken seriously.
The most annoying thing is that there are so many possibilities in terms of vegetarian and even vegan options. But BA and other airlines just don‘t care.
I strongly suggest that you complain via the ba.com feedback form.
In the future, if you have many upcoming CE flights, I sugget that you try to vary the special meals to get some change, like the vegan meal (sushi) or asian vegetarian meals.