There are so many bad reviews for this movie, you would almost feel like there's nothing to add.
Aside from the extremely toxic plot about an overbearing mother with borderline personality disorder and a daughter with poor boundaries, there's another reason this movie is unequivocally bad.
I'm talking about the insane over reliance on Diane Keaton's physical comedy. Considering that this is a rom com, there's a wild amount of screen time devoted to us watching her character be unable to perform basic functions. She can't operate a computer, she can't drive a car, or use a navigation app. She just can't do anything without breaking it, but this schtick detracts from the extremely thin plot line and fills some minutes, I guess?
The other thing that makes a movie bad is casting a pop star in the lead role and then inserting inorganic scenes just to have her sing. It just didn't make a lot of sense here. It was fine in A Walk to Remember because that was a beautiful love story about a girl with leukemia and her and the guy were in the school play.