The facility of Groups is really quite powerful. Although Groups would, indeed, be even stronger if they were dynamic (or auto-updating) there are ways to use them for what the posters above wish to filter.
Consider creating a custom fact, prossibly set to NOT export via GEDCOM, that identifies whether an individual meets your criterion for inclusion in your web page. You'll only need to do this once for each individual (unless there's a reason for an individual's status to change). Whether the fact should have two or more possible values (includeA, includeB, DONTinclude, etc.) will be part of your early decision process in considering how you will use this custom fact. For instance, if there are a relatively small number of individuals to be excluded, it will only be necessary to create the custom fact and set the value of DONTinclude for those individuals. Then define a group for WebExport. First select all individuals, then unselect those containing the DONTinclude custom fact value. If you keep the constituents of the DONTinclude set up-to-date as you continue with research, then re-generating the WebExport group before making the GEDCOM should be easy.
As always with comprehensive research, careful planning will pay dividends in the future.