You must have built the solution at least once before removing poll, survey, webstore. On post build the UI projects for those features copy the sql scripts and setup files under Web/Setup/applications
You can delete the files under there for those features and if you have removed those projects then they won't re-appear.
Still most of the features (Blog, Links, Calendar, Forums, etc) are built into the core. At some point in the next few months it is my goal to remove all content features except the Html module out of the core and into a separate group of projects so that a minimal mojoportal can be packaged more easily.
I plan to create projects:
mojoPortal.Features.Data (5 versions)
and move all the features like blog, forums, polls, surveys into those projects. It still won't be as granular as possible because you will have to install all or none of those features, but I don't want an explosion of projects that would happen if each feature was in separate projects. It will be unwieldy having that many projects in a VS solution.
The goal is to make it such that if a developer wants to package a minimal mojoportal with just their custom features and html, it will be possible to do that.
Hope it helps,