This is basically the first and most common objection laypeople have. (In fact, this comes up in every single thread on HN about DM, not exaggerating.) Believe it or not, scientists have thought of that as well. They tried, and nothing fits the data as well as the standard model.
The trope is so common that there even is an xkcd for it:
The trope is so common that there even is an xkcd for it:
https://www.xkcd.com/1758/