It's true that raising taxes on the wealthy won't, by itself, solve the long-run deficit problem. But it can still contribute quite a bit to the solution:
...Returning the average tax rate on the top 1 percent of taxpayers to its 1996 level of 29 percent could raise about $100 billion a year, or $1 trillion over the next decade.
By itself, of course, that wouldn’t solve the country’s long-term fiscal problems. ... But $1 trillion over ten years is real money and would make a real dent in the deficit.