I do agree that a 10-50 12 speed cassette on a mountain bike can give you all the climbing you need, even if you have to go with a .6:1 low ratio by running a 30t chainring. In my experience needing anything much below that will be tough to keep the bike in an upright position.
Even in a road situation running a traditional 80’s triple with a 50-40-30 and a 13-34 freewheel, you are better off on both ends with a 40t chainring and a 10-50 cassette.
The 40t chainring with a 50t cog is still better for climbing than a modern road setup with a 30t granny and a 36t cog.
John