In retrospect, Clinton wasn't the worst president, but he wasn't good. He was unfulfilled potential (his wife probably says the same), but way better than Bush or Trump. Consider:
In terms of foreign policy, when the former Soviet Union needed help, he gave them the middle finger.
Multiple times. This directly led to Putin (and Bush made Putin many times worse). His China policy turned out to be awful. Giving "most favored nation" status to dictators without extracting human-rights concessions is the wrong path forward. We should reduce trade with evil countries, not increase it (in his defense, it was more difficult to predict at the time). He had a habit of ignoring problems like Kosovo until they got out of hand, then getting involved in ways that nobody understood, thus thinking he was wagging the dog. Black Hawk Down happened during his time.
In domestic politics, he quickly gave up on healthcare, and turned into a fiscal conservative. He implemented a lot of Newt's "contract with America," including deregulation which led to the Bear Sterns disaster. He gave the FBI and police too much power, which led to disasters like Waco and Ruby Ridge (no sympathy for those two groups, but it was a sign of a police force with too much power and too little competence).
After the 1993 WTC bombings performed by the nacent Al Qaeda (not yet named), Clinton failed to take the threat of terrorism seriously.
Clinton was a smart, charismatic guy with a lot of potential but failed to turn it into a great presidency.