I'm 50 next year.
When I was younger I always had big parties but the last 'good' one I had was in my 20s, pre children. I threw a party for my 40th but it was a real damp squib, I made loads of effort, got invites printed, arranged food, drink, decorations and invited 80 odd people (including a lot of extended family. Only about 20-25 turned up in total including children, none of my relatives and only 2 close friends. In the end it was a nice enough night, but not the evening I thought I was going to have. Thankfully I'd not hired a hall or anything which would have been hideously embarrassing. I just remember feeling really disappointed.
So now it's nearly 10 years on and DP (we met a year after my 40th, so he wasn't witness to that disaster) asked if I'd like a party for my 50th. He'd happily arrange it all, invite anyone that I want there, do the food, etc.
But at the risk of seemingly completely ungrateful I really don't think I do want a party, it feels like it will just be as bad as last time if not worse. There's frankly even less chance of people turning up than 10 years ago as I've not been great at keeping in touch especially since Covid. I'd love to have a massive party like I used to in my 20s but I know it won't happen - put simply I don't know enough people any more, DP doesn't really have any friends so it's not like he has loads of people to invite to swell numbers either.
SO YABU - have the party even if it's only for a small number
YANBU - don't do it and find another way to celebrate instead