Hi M.,
To answer your question, yes, I LIKE building and playing with Legos. I don't LOVE it like my 9 yr. old son has for the last 5 yrs. What I really LOVE about it is knowing that this type of play is so beneficial to his brain! When a person follows the plans and builds the Lego creation, in the end they will get an end result that teaches them to pay attention to details and follow directions. If a person creates their own Lego creation without plans, that too is very good for the brain, as it stregthens the creativity part of the brain. Think of all this Lego building as baby steps toward a future engineer, architect, etc....
I think it's okay that your son knows that you don't LOVE Legos like him, but I still would encourage you to build with him sometimes and show enthusiasm .... even if you have to pretend to do that! Do you have an Lego enthusiasts in the family or would a neighborhood boy who's a few years older like to come over once in awhile to build/encourage your son?
Or have you ever considered a "Mother's Helper" to play Legos with him while you attend to your other kids or some cleaning? I still rec. that you interact with him when he goes for the Legos, but maybe someone else too such as a neighborhood kid, older nephew, older niece, etc... would be good too. My 9 yr. old son now teaches/encourages his younger cousins to build with Legos and he has also increased my daughter's interest in Legos.
There are so many different series to chose from in Legos. Maybe you'd like it more if you were building different things. Go on Lego website and see if anything would interest both of you.
I loved playing pretend play with my kids when they were younger. You mentioned that you love tea parties, dolls, etc... I'd suggest changing it up a bit to include your son. He might like pretend play too if you invite him to bring his stuffed animals, action figures, etc... to the table for "restaurant time." I used to be the waitress and my daughter would bring her dolls to the "restaurant" and my son would bring his stuffed animals, Lego figures, etc... to the "restaurant". I would change the name of the restaurant and change my name when we played. I could get them their lunch served while still playing with them and it felt good that they enjoyed it so much AND I was instilling an opportunity to increase their creativity because they told me so much about the character they were pretending to be. As the waitress, I asked them many questions about them. (They had different names too. lol!)
I would suggest reading about the left and right hemispheres of the brain as that information might direct you to ideas for play that you AND your son could actually enjoy.
I hope this has helped some.
J.