Professor who I requested an LoR from told me to look for someone who knows me better, but would write me one if I couldn't find anyone
If someone suggests you find another person to write for you it is advice you should take unless you have no other options.
The best letters come from people who know you well enough to speak both positively and enthusiastically about you and your prospects. This professor has some reservations.
But in the case that you really have no other options, then try to follow up with them. A mediocre letter might even be worse than no letter at all, but it is hard to say.