As soon as we see news about russians bringing literal scrap to the Ukraine frontlines, such as the BTR-50 from Khrushchev times or MT-LBs with 2M-3 straight from WW2 era, we can often here the point that "russians still have lots of such equipment and they can keep fighting on it for a long time."
Indeed, the BTR-50 is not the most archaic weapon that can be found at russian army's storages. In one of its earlier articles from October 2022, Defence24 estimated that russians might have 100 to 500 T-55AM tanks, at least several PT-76 from Vietnam war times, a few hundred BTR-60, and a few hundred M-30/M-20 guns back from WW2 in reserve. We can rely on this assessment since the authors have already predicted there were at least several combat-capable BTR-50s that the russians could send to the front line.
Actually, russians were keeping all these rarities, including the T-62s, BMP-1s, and MT-LBs not for a long lasting war of attrition but for a "swift and victorious war" achieved by throwing lots of cannon fodder. The thing is, russia has inherited the Soviet mobilization system which prescribes that all these hundreds T-62s and MT-LBs were to wait for at least the start of the "partial mobilization" in autumn 2022, for a rapid significant growth in numbers in the russian army. Instead, they started to send them to Ukraine in summer 2022 already, in small batches, just to cover the losses of the invasion force contingent.
As a result, regardless of the numbers of military equipment either in the ranks of the invasion force or at the warstocks, the russians could not use them to gain a decisive advantage over Ukrainians to achieve at least one of the goals they have set for their military campaign. For example, they still haven't managed to "reach the administrative border of the Donetsk region" in southern Ukraine.
Then, we also often hear a counterargument: "the Armed Forces of Ukraine use Soviet equipment, too, so they are doing just as bad as the russians."
On the one hand, it is true, and the Ukrainians use some even more exotic weapons made of MT-LBs. Another thing, however, is that this kind of equipment was used not only for covering losses but also for the growth in numbers, so that the Ukrainian army has grown times bigger, according to estimates.
There is also another notable weapon based on the MT-LB chassis, an improvised MLRS that fires unguided rockets usually installed on attack helicopters.
We should also recall the rare MT-LB-AT with a unique turret for a DShK heavy machine gun that helped the Ukrainian forces to reclaim the territories in southern Kherson region.
Speaking of rare and unusual tanks taken from storage, there were these T-80UD tanks seen in advance echelons during the Ukrainian counteroffensive in the Kharkiv region, northeastern Ukraine.
The nuance is that after the collapse of the USSR, Ukraine inherited only 60 tanks of this type that were put to storage back in the 1990s and remained there until at least 2022, because the first ones in the queue for recovery were the T-80BV.
We should as well recall the rare 9P148 Konkurs anti-tank missiles on the BRDM-2 chassis seen in October 2022 in the ranks of the Ukrainian army.
There are sometimes comments reminding that Ukrainians are forced to use old SPG-9 and S-60, although in fact the Ukrainian army is using even more archaic weapons. For example, the Maxim guns in variations and modifications or D-44 and D-48 cannons from the 1950s of a non-standard 85mm caliber.
All these inventions made by Ukrainian soldiers show the two sides of the same coin. On of them being the problem faced by a country by a smaller military and industrial capacity manifested in the shortage of weapons, and the other is how proficient are the Ukrainian military in using the resources at hand. Because what we have seen so far is the large variety of weapons with different functions and applications which can facilitate both repelling russian attempts to advance and Ukraine's own counteroffensive operations.