Obama promised hope and change... and then didn't deliver much beyond being Bush's 3rd and 4th terms. It's a betrayal that we still see today with "both parties are the same" rhetoric. He disbanded the progressive movements that helped get him elected immediately after becoming president and while as a constitutional lawyer he didn't want to overstep the bounds of the executive branch, he didn't even use the "bully pulpit" to try to get his supporters to make their congressmen do anything beneficial.
His crowning achievement "Obamacare" was a bandaid on a gaping wound, and now most healthcare debate centers around how to keep that bandaid on instead of the gaping wound itself that has become worse than ever.
Citizens United allowed infinite legal bribery. That was the supreme court, but he did nothing to fight it. Worse, he just let the republicans steal a supreme court seat to make sure it could never be overturned and that the supreme court would do far worse.
Snowden revealed that the federal government was using various loopholes to violate everyone's 4th amendment rights. Did Obama give him a pardon and put him in charge of reforms? Haha, no, exactly the opposite.
Did he support the working class with Occupy Wall Street? Of course not. He was firmly on Wall Street's side.
He let Russia take Crimea setting the stage for the current Ukraine war. He knew Russia was influencing our elections and our media and did nothing to stop it.
Pretty much the only reason that his term is looked upon favorably is because the presidents we had before and after were so much worse. This country would be better if we didn't even have a president, and Obama basically was that guy. The people are still so desperate for "hope and change" but now it's an uphill battle for anyone making that promise because Obama failed to deliver so massively.
Sidenote: Keeping inflation at ~3% for 8 years was really nice though. Having the price of everything more than double thanks to the bad policies of double Trump terms really does make a do-nothing president look like a dream.