Not entirely true. That's why light, FWD cars are pretty good in the snow. Less inertia means less chance of getting stuck.
Edit: Years ago a friend of mine bought a Yugo as a winter hack. Hideously bad car but it was fantastic in the snow.
Light FWD cars are pretty awful in snow, but are better in it than RWD cars, in part because of the greater mass over the driving wheels. They’re ok on slippery roads but don’t have the inertia to continue in snow as well as larger vehicles.
Basically it depends on what you’re discussing. A small, light vehicle will stop better on ice because it has less inertia (all things being equal - eg tyres, driving/brakes), but will struggle in deeper snow, where momentum and ground clearance helps massively.
You see that all the time here, small salons struggling through 8” of snow, while the larger, heavier, higher vehicles brush it off and drive almost as normal. Again this is assuming similar tyres and people that know how to drive for the conditions.