But usually the workers are secular, whose transgressions are not considered transgressions and whose commandments are not considered commandments. In addition, operating the pool usually does not directly involve any prohibited labor, at least not directly. After all, many hotels intended for the religious public also have pools.

First of all, you can’t know that all the workers are like that. Second, in my opinion it does involve prohibited labor (using electricity, pumps, etc.). I would also check carefully before using it in a hotel (the kashrut supervisor watches the food, not the pool).
A secular person’s transgressions may not be considered transgressions, but when they are done for your sake, it seems obvious that it is still forbidden.

Do you mean that there may be religious people who work on the Sabbath? Or perhaps you mean traditional Jews who work on the Sabbath, whose transgressions are considered transgressions?

As for the prohibited labors like using electricity and pumps, presumably those violations would be done whether I came to the pool or not. That is, these are labors done for all the bathers, not for each individual specifically. Is there room for such a distinction?

I mean someone who is not an atheist and accepts the giving of the Torah. He desecrates the Sabbath because he is traditional, or because of temptation, social pressure, financial distress, etc.
There is room for that distinction, but a commercial business operates for all its customers. With the electric company, where the action for others is permitted, perhaps one could tag along with that, but here there is no permission for anyone.

Regarding what you wrote here:
"A secular person’s transgressions are not transgressions, but when they are done for your sake, it seems obvious that it is still forbidden."
If the actions he does in order to operate the pool are not transgressions, why should it be forbidden? How is that different from a non-Jew or a minor?

Actions done by a non-Jew for your sake are also forbidden. As for a minor, there is a prohibition regarding a minor who acts with his father’s intent in mind (Yevamot 114), and logically it seems that there is also a prohibition on an act he did for your sake. If he does it for your sake, he is like your agent, as if you had done it yourself (only rabbinically, of course).