I think reading MiL threads on MN must be very dispiriting for mothers with sons.
Try to remember that MN only represents a relatively small and very skewed sample of the population. People are much more likely to post if they have a problem with their MiL than to say "Actually, she's fine and I like her".
My MiL didn't like me especially because DH and I lived together (in the late 1980s) before getting married. She was quite old-fashioned and was terrified I'd get pregnant. We managed to get along appropriately though.
She didn't take much notice of older DD when she was born because her own daughter had had a baby a couple of months before. We still managed to get along though.
By the time I had 2 DDs, she turned out to be a brilliant GM for the toddler stage and my DDs adored her. I would say I got to love her too, because it's easier to love someone who obviously loves your children.
So for the majority of my marriage I'd say we got on very well indeed. My DDs had a very loving relationship with her which benefited them (and her, I hope!) enormously.
I'm sure if MN had existed and I'd posted about some things that happened/were said in the early days I'd have immediately been advised no/low contact and she would have been called names.
So glad we just persisted in just trying to keep getting along. Ultimately it was a relationship that proved immeasurably valuable to my DDs and I got a lot out of it too.
DH was probably quite relieved as well.
My DDs are now married. One is low contact with her MiL because her husband is and I understand the (quite extreme and relatively unusual) reasons he has.
The other gets on really well with all her in-laws as, I'm sure, do the majority of people. You just don't read about it here.
Never forget that MN isn't like all of real life - just a little section of it. Not unimportant, but not necessarily representative of the majority.