One of the greatest presidents? I don't think so. He criticized Martin Luther King, Jr. for his impatience in demanding equality. Only Kennedy's successor, Lyndon Johnson, had the political will and muscle to force important civil rights legislation through Congress.
And Lincoln in his time publicly declared his total opposition to equality for black people, and his dream was to send all black people to Africa. Yet he is viewed as a hero on civil rights.
You show a shallow understanding of the situation. Kennedy was a radical for civil rights - which doesn't look like it by today's standards.
There are some things to understand. One is that he won a close election at the height of the cold war, when the country had demands who it wanted for president. It had just some out of McCarthyism and would have picked Eisenhower over JFK if Republicans hadn't prevented it by limiting presidents to two terms to spitefully react to FDR. They demanded a 'cold warrior' and were hostile to more than very mild civil rights.
Kennedy had a strong Democratic majority on paper, but not in practice. The south was violently a one-issue political faction fixated on war on civil rights. Filibusters were almost exclusively for southerners to fight civil rights. The only way JFK could get any of his important legislative agenda on many issues was to unite people from non-Southern Democrats, with Southern Democrats, and/od Republicans.
And the Southerners told him directly - push a civil rights bill and they would kill all of his bills. It was a very real threat. His presidency and the national good of his agenda were under threat from that. Things from food for the country to economic policies to his most cherished bill against nuclear weapon testing and a lot more.
He did not become president intending to be a civil rights president, but he became one. Polls - I've see the Gallup polls of the time - had the country saying he was 'moving too fast' on civil rights. So he lacked both public support and votes in Congress to push a big civil rights bill. He was well aware of the political demands around the issue.
And yet he became a determined civil rights leader. The fact he wasn't right alongside King doesn't change his being a radical for civil rights. A top King aide was gay and asked King to fight for gay rights as well as black rights; King told him no, that he had enough on his plate and couldn't take on every injustice. Does that mean King was not a civil rights leader?
In that situation, after a slow start, by 1963m facing a re-election campaign, JFK did the incredible choice to push a civil rights bill anyway, despite the political harm. It's not as if he couldn't wait; he recognized that his desire to leave Vietnam had a big political threat to him, and he ordered the Pentagon to plan the withdrawal for 1965, after he was re-elected. But he didn't wait on civil rights.
The odds weren't looking good for his bill - or others with the Southerners going to war with him. JFK gave a national television address to argue to a country opposed to his civil rights push, why they should support it, putting his neck even more on the line politically and 'the first time a president had made civil rights a moral issue for the country'.
For a century after the civil war, the country had maintained discrimination. But when LBJ became president, he decided to support JFK's agenda. And he shocked people by being a Texan fighting for the civil rights bills. And he told Congress that the best way they could honor JFK was to pass them. Basically every Southern politician voted no, but most Republicans voted yes, and they passed.
It was an incredible event and JFK did incredibly at supporting civil rights, by his third year, moved during his presidency as his brother the Attorney General fought civil rights issues over and over, such as the Famous confrontation at the University of Alabama to register the first black students with Governor Wallace standing in the doorway blocking them, with Kennedy having to send the national guard.
If you just want to judge JFK by today's standards, he'll look bad; and that's absurd to do.
But he was (eventually) a historic leader on civil rights, breaking the century of inaction, arguably the strongest president on the issue in history in terms of his leadership to change the issue.