Well, yes but. If we are in the world of Engineering and not Magic, we will always have a requirement for payload. If that payload includes humans it will be enormous and, even if the ejected mass can be small, there is still a need for Energy. Solutions will be there, eventually (we have to believe) button one will hang around until fusion is off the shelf in the way that Kerosine and Oxygen are, today.
And you need to remember that final speed is not the only consideration. In the real world of space travel, where you are is as important as how fast you are going. I can't believe that the basics of space navigation will be any less relevant of the foreseeable future. Getting close to the Sun involves both speeding up and slowing down and a vast amount of energy, despite you're going down into a potential well.
Then there's always the problem of getting back . . . . . .