Less harm is better than more harm. It’s also impossible to walk around without ever stepping on insects, but just because some harm is inevitable that doesn’t mean I should walk around and slaughter everything that I can find.

Agreed, it then becomes a decision about the cost/benefit ratio of how you spend your time/energy trying to reduce harm.

That doesn’t mean that veganism is ‘perfect’ in all aspects. Who knows - maybe in the future we’ll find ways to produce healthy and delicious food straight out of air and electricity without any involvement of living organisms and thereby further reduce harm. But for the moment doing what we can would be a huge step forward.

Veganism might not be the maximally effective activity from an ROI point of view.

I personally see it as a "doing what we can live with" as opposed to "doing what we can", the difference being the impact personal decisions have on the choice of harm reduction activities.

It's borderline pedantry on the face of it, but the distinction is important for me.