I am grateful to the people who do the PTA stuff, and I don't complain about them, but I don't do it and I have little truck with anyone who gets sneery or huffy with people who don't. Yes, maybe it's "tiresome" that it's always the same people who do it, but I'd guess that's because they are the people who like/are good at that sort of thing and have the time. Or, in some cases, being a bit less charitable, because they are pushy, bossy, queen bee (or king bee, I know some) types who like the idea of being in charge and cosying up to the staff. (But I realise they are not all like that.)
Anyone who gets shitty with those who do not do it should realise that some people really are too busy working, looking after preschoolers, caring in other capacities etc - or are too shy and intimidated to get involved. Those people probably far outnumber the "lazy" ones.
Or they are like me and know they would be useless. I am crap in committee situations, I hate longwinded discussions and group politics. I am an efficient, autocratic "doer" who likes to just get stuff done. On my own. In meetings I would get impatient and probably cause offence, and I always find I disagree with what 90% of other people think so that's a non-starter right there.
OTOH, there are other ways. I do help the school when there are specific skills needed, and I make donations that I have a supply of through my business (not wanting to out myself). I don't do this publicly but the HT knows and it means she recognises me.
I will sound Machiavellian saying this but I think there is good reason to be "in" with your child's school. It does do you some favours, even though it shouldn't really, and with a child with SN it's helpful for me to be able to get the HT's ear when necessary (though I don't abuse that).
But, you don't have to do it by being a PTA queen bee. To anyone whose DC are first starting school I would say, unless that committee/organising stuff comes naturally, just take it slowly and keep a low profile, and find ways to be helpful that you can manage. And if you can't manage, that is fine.