The reason the post has attracted negativity is the phrasing making it all about reaching a financial target - have I spent enough?
That's what's so wrong (subjectively, I know, it's an opinion but a widely held one).
If you have a maximum budget that's a practical matter, and is what it is, you work with it.
If you have older children or teens who know what things cost and are prone to jealousy you may choose to spend the same amount on each child, meaning if one needs a laptop for school and as a family this would be a Christmas present item, you spend similar on the sibling even if they don't have a specific need. This can be the sensible pragmatic approach in some families.
However getting cold feet about not having splashed enough cash on a 6 year old? The child doesn't know how much you've spent, and doesn't measure your live or their own excitement and happiness in pounds, and shouldn't be encouraged to!
Is it ok to only have 2 presents under the tree? That seems like something which, if you're in a financial position to buy more but have no family buying for your children you might ponder... The child has the Nintendo switch, but they're 6, perhaps wrap the game seperately if possible and wrap some chocolate, a couple of books, pyjamas with their favourite character if they'll consider that special, some craft materials, all in seperate packages so they get the thrill of multiple packages.
It's the "I've only spent X amount, I'm getting cold feet" which provokes a visceral reaction. "My 6 year old wanted a Nintendo switch and I've been able to get that, but is it ok to have just one present under the tree at 6 if your parent is in the happy position of having the disposable income to buy a few more little items?" Is somehow less insane than "I've only spent £160, is that enough?"
However having a minimum