You can get better experiences by adding mods like "Rush Hour", "Realistic Population and Consumption", and "Traffic Manager: President Edition". General consensus though is that Skylines prioritizes "pretty" over "realism", which I'd agree is generally true. It's still the best current city builder, doubly so with mods.
> for example, who does a city of 50K need a mass transit system?
There's 2 reasons for this I'd say. The first and most significant, is simply people suck at planning traffic layouts, and this game is much more punishing than other city builders exactly because it simulates every citizen. One bad driver merging can back up literally thousands of other vehicles, which propagates it's way to other exits and intersections, just like real life.
This is made worse by citizens just being shitty drivers (even more so than reality) and not following traffic logic very well (merging across 3 lanes at the last second over and over!) and the inability to customize intersections. Traffic Manager: President Edition is an amazing overhaul of this system. The UI is a bit clunky, but you can set individual turning lane rules, timed traffic and pedestrian crossing lights (even timing rules that span several intersections!). Adding well timed traffic lights has turned huge messes of downtown areas of mine into very reasonable looking traffic, without needing to rework the roads or buildings.
The top post on the game's subreddit is a guide by a traffic engineer [0] and their city has an amaaaaaziiiing traffic flow.
But secondly, it's still a game and so it can't perfectly capture real life. A big part of why traffic is so much worse than real life is the time scale. A real world city may have 50x more people going to and from work than Cities Skylines, but they also have 50x longer to get there. I can't find specific numbers, but if a citizen doesn't reach their destination in just a few minutes they are either reset or may lose that job (or both). I know people who have a 90 minute commute, this is longer than an entire Skyline's citizen's day.
The traffic system by default also isn't tied into the day/night cycle (day/night was added to the game in a later patch and fleshed out more with an expansion). So citizens leave for work/school at all times of day making the traffic feel more active than it should be. The Rush Hour mod fixes this, for example, and at 9am you'll have disgusting backed up traffic and 3am an ambulance can cross your city in seconds because streets are barren.
Still, a good rule of thumb from C:S communities is to multiply your population by 10x and that's how large of a real-world city matches yours. (For example my 250k city runs more like a real-world 2.5million city).
> Garbage management has issues too.
My biggest problem here is that services like garbage and police don't seem to give a crap how close something is to them. My current "city" is a mountain valley with a busy downtown and dozens of little satellite towns in the mountain ridges. Constantly I run into problems like a fire in a small town, but instead of sending a firetruck from the local station, one comes in from downtown, and all the local trucks are sent to deal with some downtown emergency. It seems to get worse as time goes on, and leaving my city up and running for over a day or so leads to a complete failure of my garbage system as trucks service houses which are miles away, yet adjacent to another landfill (which is also servicing houses miles away rather than nearby).
The Rush hour mod has a setting to make Cims only search for jobs and goods locally, which works great but doesn't seem to affect the services in any way. I'd love some way to enable that, or set a max-distance-from-base for service vehicles, or not allowing cross-district service usage. Anything really.
[0 - content post] https://imgur.com/a/WdJim
[0 - reddit thread] https://www.reddit.com/r/CitiesSkylines/comments/2zfx70/if_y...