Zyroxa is right. I for example watched this for quite some time now and, although being reluctant to go for 0% variable fee, I now also took this step. You are completely right with your assessment of being unable to survive long term like this. The problem for smaller pools is: Delegators, at least right now, go with either large pools (consistent block production due to the large stake - and “so many delegators cannot be wrong”) or they sort for “lowest cost” and choose one of these pools (which usually are larger ones). As there is a minimum fixed cost of 340 ADA each epoch, setting the margin to 0% is the only option smaller pools have to improve their ratings slightly in this respect.
So, until pools have reached a certain size to produce at least 4-5 block(s) per epoch (=steady returns for the delegators), one can either chose to stick to principles and keep the 1-5% margin or join the “race to the bottom” and hope to be able to convince delegators one for one in the future I came to the conclusion, that the latter is not problematic as long as you are transparent about it and tie your 0% offer to a amount of stake you want to gain instead of a specific date or so.