1.8 average rating on Letterboxd? Ouch! I agree it's not good, but damn that's low.
Leslie Nielsen is definitely the best part of the film, he plays the titular character very well. Jennifer Garner is also involved, but the support cast are all rather slack. The premise isn't, at least in my opinion, the worst I've ever seen but it's certainly pretty lacklustre and messy.
I don't actually think 'Mr. Magoo' is that awful though, except for the scene featuring brownface of course. Overall, it's a simple watch - one that doesn't take much attention. Probably worth watching only for Nielsen, and perhaps the dog.