Honestly, I understand how you feel. Just remember though that most of the parents that do talk , are only doing so because their kids are friends and acquaintances at best, it can be a bit forced! You are all together because your kids are in the same class, often they are people you wouldn't be friends, or ever associate with normally. I also hate to say it, but to some, the school is literally their life. I think when you have friends outside, work/hobbies etc it doesn't matter as much.
I think it is sometimes down to luck as well, if you connect with the particular parents in your child's class. In my older child's year i'll say hi, or make small talk rarely but I'm usually standing on my own (which I prefer with this lot if I'm honest). I can't be bothered with awkward forced conversation. A lot of them live very close to each other, and their dcs play out together etc. It was such a clannish year group from the beginning. The school had to split the classes up, which is something they don't normally do! The parents would pick and choose which kids went to birthday parties at 5, based on parents and not their dcs; it was awful, and unhealthy.
However now, even the parents that used to talk all of the time look like they can't be bothered to talk, and have irritated each other lately, though! I had pretty much given up, but after 3 years I have ended up talking to acouple, always seen their faces but it just hadn't happened. We had the "why haven't we talked before" moment. I also think they've gotten a bit sick of each other, and haven't been quite as close as they appeared.
The parents in my younger child's year are lovely, and much more on my wavelength. I am lucky that the couple of Mums I instantly connected with at the beginning have dcs that ended up being my dc's best friends. This happened organically. The other parents also are decent, and will all say hi, and include everybody. It is the complete opposite to dc1's year group!
Please be kind to yourself op, I always think if it doesn't happen naturally they're not your tribe! There is still time, and if not don't worry. There will be very few that stay in touch after primary school!