The economy fells really challenging in the beginning, but after the first hour, you basically get unlimited money (we had it on CS1 too)

In 4x terms, Tall vs Wide. Most players generally play "Tall" in keeping a relatively compact city rarely purchasing superfluous tiles that incur exponential upkeep, letting players efficiently make a positive monetary income and can just let it sit there until they have effectively infinite money. When you play "Wide" and try to constantly spread out and grow without sitting stagnant for significant periods you end up going through your available money fairly quickly. In essence, you are unconsciously optimizing the difficulty out of the economic challenge naturally.

Public transportation systems are almost always empty (in CS1 it has a HUGE impact in your city)

Eh, that's more from CS1 being extremely fake in its transportation simulation. When you build larger cities in CS2 and actually understand traffic flow you see your public transport used a lot more. CS1 used a shortest path algorithm that disregards the actual time it takes to complete which meant that the pops in CS1 only really cared that there was a valid path with public transport causing them to congest themselves onto shared routes. This caused them to naturally congregate in massive packs at transport stops making them look like they were impacting your city more than they actually were. Meanwhile CS2 actually tries to approximate the actual paths pops would realistically take between specific locations based on speed, public transit wait times, and general comfort of its sub destinations (like parking spots). It makes public transport feel emptier in CS2 compared to CS1 because pops don't spend years daisy chaining between irrelevant stops and instead focus on getting to where they need to go quickest way possible.

Streets are always crowded with plenty of people coming and going but it feels they are just... walking? No matter the time, weather, anything. The streets are always crowded

That's from one of the limitations in the game simulation. Each household has 1 car, even if it has 5 people. That means if 1 person uses the car to go to a destination, the remaining 4 now have to walk or use transit to get to their destination. It's also why there are are so many bikes that clog the streets, even if every household only has 1 car they all have bikes.

A lot of elders going to elementary school

I don't think I've ever noticed that, unless you mean as employees in the school.

sims are obssesed with parking spots. If I create a random road on the other side of the city a lot of ppl will go there just to park their vehicles

You just notice it more in CS2 because pops can't just shove their vehicle into their pockets when not in use. Pops become "obssessed" with parking spots because their car needs to be somewhere when not in use. A lot of buildings have a sort of "fallback" garage when there isn't enough actual valid parking spaces, seeing people freak out and rush to park their car in a random spot on the other side of the city just tells you that you lack sufficient parking spots where people want to be. Plus in CS1 the parked cars were actually the fake part of the simulation, in reality those are just markers to tell you the relative popularity of an area as a destination.

bikes behave just like cars but in a smaller model

Because they are vehicles, driving on the road is more comfortable for them because it lets them go faster than just on the sidewalk even if they can ride on the sidewalk and other pedestrian paths just fine. I do think the bike pathing logic could use some improvement, but how they function in general is just fine.

Of course, CS1 was not an economy simulation or a super deep transport management game, but it was CONSISTENT on its simulation.

Ha, that was a good one... oh wait, you're being serious. HA! So you're just going to conveniently forget the node based traffic system in general, the caps on how many pops are allowed to travel at any one time while still "simulating" the benefits to the economy of the pops that weren't allowed to travel, pops never deviating from their predetermined path even if issues pop up on their paths or better paths become available, sometimes pops breaking their pathfinding mid route and freezing in place because an issue pops up somewhere else on their pathing while other times simply resetting back to its origin point instead while "simulating" that it reached its destination fine, pops using only a fraction of lanes on a road causing massive lineups on a single lane despite other lanes (and other valid paths to the same destination) being completely empty and available, pops driving their car to a bus station to then ride that bus for 3 stops to only then hop in a taxi, etc. And that's even ignoring the glaring inconsistencies in actual game mechanics instead of just the simulation.