The main reason for fasting and other forms of ascesis is, ideally, to break our attachments, or else, when that proves too difficult, at least to make us more keenly aware of them than we ordinarily are. So the first question we have to ask ourselves is: To what am I most strongly attached? It may or may not be to meat and other animal products, or to food in general. In which case, keeping the dietary rules of Lent is, I agree, not really the point.
More important is an inward ascesis. What I have in mind, in part, is the wresting we’re obliged to engage in whenever we confront, not our attachments to what the body prefers (as for example food and sleep), but our wish to be right, to be thought well of, to get our own way, and so forth. Whenever we catch ourselves inwardly judging others, growing impatient at the person running the cash register at the grocery store, relishing praise, nursing the feelings of self-pity and resentment, we have an opportunity to “fast”, to take a step back from our inward state.
Given this, I would say: No, doing “what I can”, contrary to what you wrote in your message, is not the best answer. The best answer is to try to do what I probably can’t, and then to watch myself, openly and honestly and without flinching, as I fail; and then—here’s the key—not to allow myself to “feel bad about it”, for that’s just the ego in yet another disguise. Watching, thus understood, is very, very hard work, but it’s key to a genuine and truly transformative ascesis.