Including poor undergraduate research performance in a masters application
I don't know about your field specifically, but in my field, you can rarely make any serious progress on research working part time for part of a school year.  This is true for professors, postdocs, grad students and and especially true for undergrads.  The point of undergraduate research is (1) to give you some taste of research, (2) to learn a few things, and (3) maybe help contribute a small amount of insight to some problem.  At least in math, it's more common that undergrad research "only" results in a learning experience rather than a publishable paper.  In fact, many research projects for grad students and beyond never become papers, and of those that do, it generally takes more than half a year.  That's the nature of research.  It's not easy.

Moreover, as you advance and mature your point of view, it's natural that you view your earlier work as naive (again, this is true for professional researchers).  That's fine.  That doesn't mean there was something wrong with what you did earlier, but just that your understanding has advanced.

Anyway, to answer your question, I would probably include lines on my CV saying you were a research assistant, and at least briefly touch on them in your personal statements.  (You may also want a letter from someone involved in one of these, but that depends on your situation.)  You're not expected to have outstanding outcomes, so you don't need to focus on that outcomes.  But it shows motivation beyond the required coursework and that you have some experience with research.