Having made such a dreadful start to the Championship campaign following relegation from the Premier League, the Blades are now unbeaten in five games.
Jokanovic said: "I am satisfied with the performance and the three points, but it's not enough.
"We have scored 11 goals (in three games), but we need to improve on a lot of things.
"I was missing a little bit of our killing spirit. A lot of times we had space and we were in the situations to try to be a bit more dangerous.
"If we want to fight for the target, we need to grow up. We made some positive steps but it's not enough.
"It's important for us to make things even better.
"We cannot stop and think that we are in a good moment. We still need to fix some defensive problems."
Sheffield United were good value for three points in a one-sided Yorkshire derby.
Hull began brightly, but the visitors took control after 17 minutes when Billy Sharp scored with an easy header on his 300th appearance for the club.
Sharp missed a penalty later in the first half, Matt Ingram saving well to his right, but it was of little consequence once United kicked on after the restart.
John Egan weighed in with a header from Conor Hourihane's dangerous 50th-minute corner to give his side breathing space.
With Hull having lost their focus, Egan put the game to bed after 61 minutes when he expertly headed home another Hourihane set-piece.
Hull improved thereafter but never looked like staging a dramatic recovery.
Jokanovic said: "I want to mark my territory. We won, got three points and scored the goals, so it's easier for my team to follow the process.
"I believe we have a good group of football players – I like my people.
"We showed some signals we are moving in a good direction, but we need to be ready for the serious work and to push hard.
"At the moment we are at half-speed. We can be more brave and have more killer instinct."
Counterpart Grant McCann admitted Hull were second best all game.
He said: "We came up against a very good team who will only get better and better.
"But, for us, we're disappointed. We need to do better, it's as simple as that.
"We've got to grow up as staff and players. Teams are aggressive but we need to be aggressive – especially with set-pieces.
"Things aren't going our way and we're all not at this level yet.
"I take accountability for it – I'm the manager – so we'll have to go back to the drawing board and go again."
On Hull conceding twice from set-pieces, McCann added: "Our best markers in the box are the ones that have probably let us down with the goals.
"We can't let anybody block us (for the second goal) and for us to concede another goal from a set-play was totally unacceptable.
"We didn't do enough and we need to work hard and start winning games, but we'll definitely get better."