Nuclear weapons require constant, ongoing maintenance if they have any hope of going bang. Russia doesn't have the assets to keep that up anymore. Their nuclear arsenal is probably a fraction of its theoretical capability.
In addition, if Putin tried to launch nukes, I doubt the other oligarchs would go along with his mass suicide plan.
If there is one thing I've learned about Russian technology then it is that in general it will operate 'good enough' to do what it was designed to do even if that means that it isn't designed in a way that we would consider elegant. Assuming that Russia's nuclear arsenal is dysfunctional or even non-existent would be a very large - and possibly fatal - mistake, especially given that it never was designed as a precision tool anyway but relied on massive overkill. You may well be right, but if history is any guide here making assumptions without hard evidence about the nature of an enemy arsenal, either positive or negative will lead to trouble.
I had a couple conversations with an engineer who worked a long career on maintaining nuclear warheads. I was rather surprised when he told me that he didn't view nuclear war as likely.
As he explained it, plutonium warheads break down over time. They create helium gas pockets and sometimes internal fractures that prevent detonation.
The solution is to reform the warhead every few years.
The problem here is that plutonium has over a dozen crystalline forms. If they don't achieve a uniform crystal, the warhead will fail to detonate due to the imperfections along the lines where the different crystals come together. This takes a ton of time and money (and often many, many attempts).
Together these mean that the warheads are getting very old and the upkeep to keep them working is huge. Russia can keep a few in working order, but not nearly what their previous arsenal would imply.
I have always wondered this. Nuclear Apocalypse scenarios always assume the ICBMs will all function as specified. Maybe they will, but it's not like you can thoroughly test each one. But I guess they don't need to.
There were assumptions that lots of missiles would malfunction or not reach their intended targets and so various cities and strategic objectives were targeted with multiple warheads from different launch sites. This led to 'overkill':
In addition, if Putin tried to launch nukes, I doubt the other oligarchs would go along with his mass suicide plan.