You don't always need a HOA, though. My dad's house is in a non-HOA neighborhood. Everybody takes care of their shit. Not a single one of the 40-50 houses has an issue with super tall grass, broken down cars, junk all over, house damage or odd colors, or bad/ugly lawns. Grass gets a little high (4" maybe, not 4'), it'll get mowed when it ain't so hot out in South Texas. Broken window? Fix that shit ASAP, it'll cost less in the long run and might even burn out your AC. Big tree limbs down? City picks up brush every other week. It's GONNA wait. My dad had 3-5 large tree limbs after a big windstorm that also knocked over the fence he shares with another house. He drug the limbs to the side of the house to wait for brush pickup, which was still a week away. Then he fought with the neighbor about the fence because of the way it's facing it's the neighbor's responsibility. Neighbor fixed the fence a week later on payday, which was a day after the brush got picked up. A HOA would've made everything worse, for no benefit, for something that got taken care of in a timely manner.
It's a mixed bag.
For one, you say an HOA would have made all that worse, but that's not at all some kind of hard and fast rule. When I say things need to be dealt with in an appropriate time frame, I don't mean the next day for something like a major tree limb. This is life, this is reality, shit takes time to get done. But it shouldn't take weeks and/or months (depending upon situation, some things take longer than others). Yes we have to wait to schedule someone to help repair something or otherwise wait until there's at least time available to do something (because most of us have jobs), and that's ignoring any potential financial difficulties affording repairs. This happens -- life that is -- to all of us. I would say that in my experience, reasonable timeframes are reasonably applied. Some things just take longer, and all of us with feet firmly in the real world understand that.
On the flip side though, if you can't afford simple repairs for fairly "normal" house repairs, then you are probably in over your head and have too much house/property for your income. Nothing necessarily wrong with that at all, that's a situation many people fall into, but it's something that should very much be calculated when you are deciding on how much home you can afford. This is what really tends to be the driving force behind any decline in economic status, or any increase in blight. People who can't afford to fix their house and/or property, and things slowly go downhill. As I said, there is nothing at all wrong with that picture on an individual scale, but when you suddenly have half a neighborhood facing that situation, blight moves in real fast. When home prices are low, rates are low, and banks are stupid, you get a ton of people with "cheap" homes that totally miscalculated how much the property taxes are, how much they should have for home repair, the increased average costs of repairs due to increased square footage, etc. When a nice neighborhood has went some years with numerous foreclosures, total market rate for the entire neighborhood drops. There are many buyers who do not want to be anywhere near a glut of foreclosed homes, for some very obvious and sane reasons.The individual families at first are likely perfectly normal folk, but over time new families moving in may bring some baggage. And it snowballs downhill from there.
And of course, HOAs suffer from foreclosures too, no neighborhood is exempt no matter how strict or hawkish. You know the phrase, "life finds a way" - well, "shit finds a way" is just as true.
One other thing you bring up is government response time. You seem to have a nice response time in your experience. This is not universally true. Grass 4" tall getting complaints (and official response before it gets much longer, which means a rapid response) is kind of ridiculous. I'm assuming there's some exaggeration in that statement, but even what most of us consider reasonable response times are routinely missed by many jurisdictions.
But also as you say, there are
plenty of neighborhoods out there that are not in HOAs and yet remain in wonderful shape. This seems to be a product of luck more than anything, these are beautiful neighborhoods that have been saved from too many foreclosures and blight. The neighbors all care. That's certainly how it should be, but is not that way in many areas. Cities can have all the regulations they want but if enforcement is slow unwanted behavior will never be fully discouraged.