I believe you are mostly arguing against a strawman (or highly editorialized, i.e. misleading headlines).
It would be beyond naive to assume that Russia would just announce "we're out of tanks, gonna call of the war now!". That is not how supply shortages affect a military.
What you instead expect to see is that the use of scarce weapon platforms and ammunition types becomes rarer, and that militarily undesirable compromises and alternatives have to be made and found (which is more costly, less effective or both).
Instead of taking massive ground in a tank offensive, the military might be forced into slowly advancing trenches and artillery; long-range guided shells might be reserved for high value targets only (instead of being blanket fired at every somewhat promising target in range). You would expect to see significantly older and less effective equipment, instead of more modern variants, more conservative use of bombardment, etc.
These are all things that can actually be observed! But they don't mean that Russia is going to lose, obviously-- this is just going to make continuing the offense more and more difficult, expensive and less effective.
You do not need to take my word for this, and you don't even need to keep up with lengthy OSINT reports and analysis to track this yourself, just consider the following: There has been significant use of Iranian drones and ammunition and lately even North Korean conscripts. I find it very hard to believe that Russian leadership pursued this as a desirable choice-- rather, it seems the exact kind of necessary alternative/compromise that you are forced into when you can not properly supply the war effort on your own (just like how the Ukraine was from day 1 forced into relying on western systems). This is especially glaring because Russia is a proud exporter of both weapons and mercenaries-- having to fall back on foreign stuff is just a bad look here.