This is a pretty wide topic, but let me start by addressing this, the West had a long-standing naval tradition and invested heavily in naval matters throughout the Cold War, while the USSR and China did not, their potential survival did not rely on control of the seas, and they invested vastly less in naval issues than the West did. That’s not to say that they weren’t innovative, the first anti-ship missiles used in combat were Soviet and their first victim was ‘Western’, the Israeli destroyer Eilat sunk by SS-N-2 Styx missiles from a couple of Komar class missile boats. Thats sort of emblematic of the NATO vs Warsaw Pact doctrine when it came to naval matters, NATO needed to control the seas while the Warsaw Pact didn’t and focused more on sea denial. This has changed drastically since the end of the cold War; Russia is well, Russia with all of its problems while China has become interested in being a major naval player in the Pacific and has drastically expanded its navy both in numbers of major surface combatants and their capabilities.
A lot of the quality vs quantity aspect of equipment as opposed to doctrine and training is an artifact of US/NATO equipment that began fielding in the 1980s. There was little to choose from between for example the MiG-15 and the F-86 during the Korean War, the F-86 wasn’t a superior fighter, it was flown by superior pilots where the doctrine and training emphasized quality over quantity. Up until the 80s Soviet ground equipment was often quite innovative and in some cases superior to their Western counterparts. The T-64, when introduced in the 1960s, outclassed any NATO MBT. The BMP was a revolutionary design in infantry vehicles, being an infantry fighting vehicle as opposed to a glorified battle taxi. It hasn’t weathered the test of time that well and suffers in comparison to vehicles like the M-2 Bradley, but it’s important to remember that when it entered service in 1966 its contemporary wasn’t the yet undreamt-of Bradley, it was the M-113.
The 1980s saw the deployment of a wide range of military hardware that genuinely worried the Soviet Union which feared a genuine shift in military affairs via technology by the West, something that was demonstrated to have at the very least some truth to it during the 1991 Gulf War where a largely US coalition military armed with the fruits of all of that money spent developing a new generation of equipment to fight the Cold War during the 1980s ran circles around a largely Soviet equipped military by using all of those things that the Soviets feared would result in a paradigm shift in military affairs. Thermal imagers which allowed Western armor to operate at night as effectively as they did during the day and dominate engagements by destroying Iraqi vehicles before they even knew they had been spotted, stealth aircraft able to penetrate the most heavily defended airspace, cruise missiles evading air defenses and striking key targets with devastating precision, systems like ATACMS able to deliver powerful deep strikes beyond the Forward Edge of the Battle Area where by Soviet doctrine follow on echelons were supposed to be moving towards the front in relative safety.
Things have changed a lot since the Cold War, but the current war in Ukraine is being fought largely with modernized Cold War era equipment. Things with Russia have gotten comparatively worse since the days of the Soviet Union, the Russian military became a hollow shell of what the Soviet military had been with equipment being retired or left to rot due to lack of funding in the immediate aftermath of the collapse of the Soviet Union, and the more recent Russian attempts to puff up its military’s image proving to have been a charade with the outbreak of the war in Ukraine. A lot of its latest and greatest military hardware is noticeable by its absence on the battlefield, either completely (T-14 Armata, Su-57 Felon, exoskeleton combat suits, even the more basic Ratnik future infantry combat system) or barely making a cameo appearance in the fighting (BMPT Terminator).
China, on the other hand, has become much more capable since the end of the Cold War, unlike Russia its economy has been steadily expanding since then. Chinese military gear during the Cold War was largely knock-off Soviet equipment that had been reverse engineered. Part of it is still somewhat Soviet-era knock off, though licensed such as the J-11 which is a license produced Su-27 Flanker while some of it is home built and apparently very high tech and high-quality equipment such as the J-20. The J-20 is probably a modern stealth fighter that is actually in service and a credible threat unlike the Su-57, but we’d probably need a war to find out the truth of the matter, not something I’d like to see happen.