TdP nailed the answer on this.
What you can do with valves you can do with transistors. Depending on what exactly you are trying to do, it can be easier or harder, simpler or more complex depending on which technology you choose.
That's his view and I think it's ultimately correct given a talented designer and little limit on resources.
My view is that if you figure cost, efficiency and ultimate transparency into the picture, SS always has the potential to win-out over tubes. If you simply desire transparency there is no case for using tubes over SS. If you want niceness, or what is effectively a flavoured take on things then tubes can be subjectively better.
IME bad tube amplifiers usually still sound perfectly listenable, whereas bad SS amps usually grate on the ear. The distortions produced by a less than wonderful tube amplifier seem less bothersome subjectively than those from poor SS. Bloody difficult to build a poor SS amp today though.