Not true at all. The risk may be overstated by some, but it's a perfectly possible outcome that must be considered.[0]
A "World War" requires an opponent worthy of a world-wide conflict, and Russia is anything but
Also simply not true. It just requires one side to start using nukes, which can also happen entirely by accident (and has come close to happening multiple times, even without a multi-year and incredibly nasty hot proxy conflict on the ground between two of the planet's largest mutual adversaries).
As for nuclear weapons, they are practically useless.
True of course, but it doesn't matter. What matters is that certain people might start to think that they're useful and/or their only choice. Which gets into the fact that we can't assume these people are acting rationally.
Also, notice how Putin and his officials talk about nuclear use a lot, but there is still zero evidence of any action
Right, but that can change at any time. It doesn't even have to be a tactical battlefield strike (which of course would be useless, and their people know it). For example, once their backs are pushed against the wall with sufficient firmness, Putin or his successors might start to think that a demonstrative high-altitude detonation over an ocean somewhere might be a pretty neat idea. Especially if they've reached a point where they have nothing more to lose, and have a reasonable fear of being outright killed sooner or later if the current situation on the ground starts to move strongly and rapidly against them.