More than only poor quality, would you drive a 50 year old car?
The T-72 tanks which is by far the most common tank in the war was put in production in 1968.
1968!
Even the latest updates are still decades old.
They are not just poor quality, they are obsolete.
PS, the T-90 is a version of the T-72, and the T-80 is based on older T-64 with T-72 features.
(granted the US M1 Abrams tank is developed in the 1980's, not much newer. Other nations do have more recent designs).
When I got my 2016 Model S, I was driving a 24 year old car I bought new, but I'm a weirdo.
Tanks, like military aircraft get upgraded over time. The youngest B-52 was completed before a lot of people here with grand kids were born, but they are still flying. They have been updated several times. Many of the T-72s in Ukraine have a 2016 upgrade kit, which ironically, was made in Ukraine. The T-73B3 is a 2010/2011 upgrade kit.
The Russians have been recycling tank designs since the 1960s, all the operational tanks have roots in the T-62 and T-64.
The M-1 Abrams has been updated too.
A lot of the problem the Russians are having with their tanks is the way they are using them rather than the tanks themselves. The T-72 is not the latest tank, but it should be adequate if used right. Tanks offer a lot of punch on the battlefield, but they are by their nature blind to small threats like infantry with anti tank weapons. Even the best armored tanks can be immobilized by a broken track or a damaged road wheel.
Early in WW II some armies tried to field units that were all tanks, but quickly found that didn't work. Between the wars the Germans figured out how to best use them. A Panzer division had quite a few infantry that were embedded with the tanks. The troops were carried in some kind of vehicle, trucks early war and later half tracks or riding on the tanks themselves. When in a safe zone the infantry would travel in their vehicles, but as soon as they contacted the enemy, the infantry dismounted and moved forward with the tanks on foot.
Infantry on foot are much better at spotting enemy ambushes and either dealing with them on their own or directing the tank to take out the enemy position. Virtually all tanks and heavily armored vehicles of that era had multiple machine guns to use on enemy infantry if they got close.
At the battle of Kursk the Germans delayed the start of the battle to complete and bring to the front a relative handful of super tank destroyers called Ferdinands. The Tiger tank came out of a competition between Porsche and Henschel. Porsche was so confident they would win, they started construction of their chassis before the competition was decided. In the end Henschel got the contract and the Porsche chassis were sitting there. The Germans, never letting a vehicle go to waste converted these into super tank destroyers with and armored box instead of a turret and a more powerful version of the famed German 88mm gun.
In their rush to convert the tanks they didn't put any machine guns on the vehicle. For the battle of Kursk they had sharpshooters riding on the Ferdinands instead. The sharpshooters quickly got wounded or killed leaving the Ferdinands with no protection other than their armor. Most were quickly disabled. The remaining Ferdinands were reworks to add machine guns and were sent to Italy now called the Elefant. It did much better with some machine gun protections and a few Elefants are museum pieces today.
The best tank in the world is vulnerable against an army with any kind of anti-tank capability if their infantry aren't operating dismounted around the tank. The US is lucky that in Desert Storm the Iraqis didn't have anti-tank squads in priest holes in front of the Republican Guard. The M-1s came charging in without infantry support and would have been sitting ducks for AT weapons. Even if the weapons couldn't punch through the armor, they could break the tracks and leave the tank disabled.
The Russians have an amateur army. Their training regime is poor, the majority of their troops are very badly educated before the army, and their commanders don't have the first clue about combat doctrine. Their military is so corrupt most officers have spent their careers either ratholing money or paying off gangsters who prey on the military personnel.
When developed country's armies have exercises, they are to evaluate doctrine and make adjustments as necessary as well as give the troops some first hand training. When the Russians conduct exercises it's all about demonstrating to the world how powerful their army is. It's a show, not an actual exercise.
Authoritarian regimes almost always front. Most are run by people with Narcissist Personalty Disorders or people with a serious narcissism problem. For narcissists it's all about what people see and the show they put on. Substance is not important. So the military is a show piece that might be able to fight off a weak enemy, but it isn't really a serious force.
Serious governments run by people who are more concerned with governing than "look at me" (though every politician has some narcissism or they wouldn't be there, for the good ones governing is more important than what people think of them), the military is supposed to actually do the job. Sometimes people ride in the military who are unqualified, but most of the time the people at the top got there on merit. They are professionals who want their military to be capable of doing the job, not just look good.
So the developed countries have doctrines they have honed for decades. They also plan for every contingency. The troops train and they do constant maintenance on their equipment so if war does come, everybody and everything is ready. Countries with hostile neighbors usually have a well laid out war plan if their neighbor gets hostile. Israel has done this, so has Taiwan and Finland. Israel has had to put their plan into action multiple times and they have won every defensive war they have ever fought.