I posted on the first page and how now come back and read the subsequent 9 pages. There is a bit of a drip feed going on by the OP, I think she's had trouble really verbalising what aspect of her mother's role as grandparent she is finding lacking.
I can kind of see where she is coming from about the Friday night thing - yes, initially it was probably a major favour that was recognised as such but since then she's had another child, the going out thing has become redundant due to the fact that her mum will only have one not the other (her choice, so fine) and its really the Grandma who is keen to keep this arrangement rather than the OP. So whilst it still counts as help, the OP would probably trade it in a second for the kind of help that may earn much less "brownie points" but go a lot further to making her day to day life easier.
I have to admit, if you were trying to finish a meal with a fussing child and your mum was sat there finished, just watching you struggle, that could be irritating, even if its irrational to be irritated by it. I have no idea how the OP handled it though. If it were me, I'd say "Hey, Ma, you wouldn't mind having DS while I just finish this would you, then I'll grab him back". And, to be honest, if she said "Um, no, I'm fine thanks", well, whilst she is in no way obliged, I suppose, I'd be pretty miffed on behalf of DS if nothing else - what kind of message would it send? But its hard to know exactly whether the OP asked politely for help or just sat there bristling.
It sounds like the OP wants help in reasonably small and low impact ways, as opposed to actual childcare, but is possibly not that great at making it happen without rubbing her slightly oblivious mother up the wrong way. That's how I'm interpreting it.
As for the community raising a child - its a lovely idealistic theory but these boards are riddled with stories of mothers who go spare if anyone dares to tell of their child, people not wanting someone to take a photo with their child in the background, a mother in law who hands a child a biscuit and doesn't see what the problem is, giving them the wrong toy to play with, they can't win! They are probably too scared to offer help. I dont mean in the case of the OP so much as generally - if anyone wants that caring sharing community feel about the place, it goes both ways and many can take, but they can't give. I think those days are over, sadly, for most and we reap what we sow.