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You must be in a state that remotely aligns with your perspectives, but many are not that lucky. While theoretically the smaller the government, the more responsive it is, US states are a great counterexample. They associate people under the same government in ways that are divorced of current economic and cultural ties. State governments are also easier to gerrymander: See the many states where the difference in direction between state level elections and the state house is well over 10 points.

Furthermore, the much lower level of oversight in states lead to more extreme, low quality decisions, often which end up with people less happy than with national level decisions. See abortion: Leaving the decision to the states led to fewer people being happy with the laws they had, instead of more. This isn't because there aren't plenty of people that want very strong abortion restrictions, but because state lawmakers in states with Republican legislative majorities are far to the right of not just the median voter of their state, but even the median Republican. Similar things can occur in blue states. And how are legislators acting when they see voter-driven referendums to change legislation? By passing laws demanding 60%+ of the popular vote to overrule the legislature.

You also talk about politicians disconnected from real issues: When I look at the laws my state representatives try to pass recently, they are either not clear 50% of the popular opinion, or focus on key things like, say, legislating high school athletics for trans students. Given that the fact that they know which part of the state votes in favor of the majority of legislators, and which parts don't, how do you think they spend the money? That's right, the parts of the state that don't vote correctly don't get anywhere near the level of investment that matches their contributions to the state coffers. After all, making sure there are fewer people living in those places is a sure way to maintain control of the state government in the long term.

So while I am not unsympathetic to the idea of more local government, States are such a poor example of 'laboratories of democracy' that in a majority of cases, the federal government works less badly. Marijuana is the rare case where things happen to work out.

Sure this works for simple stuff like this.

It does not work when one state wants to keep slavery legal.

Like everything, a balance needs to be made.