As a geographical locator, it's not good enough. And I'm someone who thinks that people who don't use a house number, preferring "Bide-a-wee" or "Crow's Nest", deserve all the mis-directed Amazon parcels they never get.
House numbers in many places aren't really suitable
A mate's old house was along the lines of "The old thing", "New Farm", "That village", "Nearest big village", "Nearest Post Town"
The post code covered all of "That village" but the village was spread out along a main road and mostly just a collection of farms branched off of it, house numbering looses it's advantages when you've not got a linear line of houses along a road but sets of the splatted all over the place.
But then the post office (who produced the system for their purposes) would have sorted all of the mail for That Village into a bag and given it to the postie that drove the route that goes there every day.
The building my office is in is off the road it's addressed on, on a "private" road, the post office and other delivery companies have no problem working out where we are and even differentiating between the two buildings operated by the health service on it from the sports center, but it's quite amusing to watch food delivery riders/drivers fail to find us because far too much trust has been put into Postcodes by their "employers".
Part of the problem is the Post Office have decided we should have a different post code from the houses on the road, and therefore we have the same post code as the old sweet factory slightly further north. It's particularly bad with Deliveroo as it means we have to wait for the rider to cross a main road before we can contact them tell them they've gone wrong... oh and we're at the top of a climb that goes up over 100.
This is where what.three.words and/or the national grid come in handy because they designed as geographical locator's rather than mail sorters.