They're not helpful at all. All households have different heating systems, that are used in different ways, also differing amounts of showers, cooking and laundry etc.
Then there's electric cars and solar panels to account for and variations between payment methods, direct debit is a few percent cheaper than pay on receipt of bill.
Then someone will be quoting their last bill, others their direct debit amount, which often bears little relation to the average amount their gas and electricity costs, the '£60 pm and in credit by £800' poster being a case in point. They either use nothing at all but for some reason overpay or, more likely, have reduced their DD amount to use up the large credit they've built up. So no indication at all as to what their bill is.
For all the arguments the price cap amount caused, it does serve a useful purpose in that if you are a 'typical' household, ie a medium sized one when averaged over the entire population, your G&E should be roughly that amount, and obviously if you are in a 5 bed house you should expect it to cost more, although probably not as much more as the OP is paying, and if you are in a small flat, it should cost less, although the amount it can go down to is limited somewhat by the standing charge which I believe is about £30-40 pm.
But yes, it is possible to reduce your usage significantly. We've cut our gas use by over a third by closing one door so we're only heating the living room and not the entire house and the outside world due to our drafty front door. We've also cut our electricity use by switching to an air fryer most of the time.