Most US equipment, in vehicles anyway, is "Soviet-era". The Abrams is from the 80s and started development in the 70s, the F-22 program started in the 90s, the vast majority of Air Force aircraft are from the 70s or 80s, the M-16 is fifty years old, etc.
The problem with the Russians is definitely not just in equipment.
Right, but the U.S. hasn't had major economic/corruption problems interfering with maintaining that equipment and also hasn't been trying to maintain Cold War levels of materiel with drastically fewer resources than it had at the time. I'm saying "Soviet" rather than "Cold War" because this is specifically a problem with Russia LARPing as the USSR despite not having the resources to maintain or field most of what they've had in storage.
The F-16s, for example, that are still flying are probably mostly Block 50/52 C/Ds, not As. Those are post-Desert Storm production, not literal 1980s airframes with a new avionics package stuck in and newer missiles on the pylons.
I am taking those stories with a mountain of salt. Ghost of Kyiv myth becomes increasingly absurd...
Saying this, the specs of airframes are secondary. Electronics inside the aircraft and quality of air to air missiles are way more important and Ukraine may be not as much behind as it seems.
Ukrainian reports seem to typically come with least attempts to provide documentary footage and evidence, as well as admitting to setbacks when they happen. Y'know, as opposed to Russia state media saying everything going swimmingly. Definitely might want to take care with the Ghost of Kyov memeing, almost everyone I've seen doing it is a blatant Kremlin bot repeating the "Nazi Ukraine" party line or openly admitting to liking imperialistic ambitions on Putin's part, and you don't come across like that to me.
Sort of related to what I said above, I think a big factor is that Ukraine hasn't tried to maintain a massive arsenal beyond their means. Just having all of their equipment in good shape, run by well-trained crews, and supplemented with modern ordinance from abroad seems to have been the formula for success here.
e: Specifically regarding the "Ghost of Kyiv" copypasta: It's overt astroturf. This is why:
1. The format is near-perfect. It's a single line with a catchy name already attached, which makes it easy to spin off iterative variants, which in turn makes it very attractive to third-party users who want to spam memes without thinking about the implications of what they're doing.
2. The message is exactly aligned with Moscow's goals: it dismisses news of Ukrainian successes by flooding any post about them with disinformation and noise that implies
all Ukrainian successes are (and here's an unsurprising season 2 recurring appearance) "fake news". It also drowns out any attempt to discuss or engage with said news. You can't have a conversation if 3/5ths of the comments are copypasta spam.
3. It emerged instantly on a wide range of platforms. This is not how memes naturally develop. Normal dissemination would start with the originator on one platform, spread on that platform, and start making leaps to other platforms where it would re-spread. This takes at minimum days, more often weeks or months in the wild. The "ghost of Kyiv" shit went from "does not exist" to "everywhere" in less than a day. If you check google search analytics the phrase did not exist prior to 2/24, peaked mid-day 2/25 or early 2/26, and abruptly fell off. Real memes don't flare up that quickly or die off so rapidly. If you look back at other memes: Ugandan Knuckles took 2-4 weeks to peak, amongus took 5-6
months, dicks out for harambe took 2-3 months, &c. and those have much broader appeal. That's a pattern suggestive of a deliberate campaign to disseminate it.
This is the sort of thing that Putin is good at.