Why do democrats think that unemployment can't be fixed within 2 years?

Someone just asked why republicans think that unemployment should be lowered within 2 years. My question is, why do democrats think it CAN'T be lowered within 2 years? I understand government doesn't create jobs other than government jobs, but they sure can influence job creation. Reagan's model worked, and when I hear people say that his method of economic recovery added to the debt (even though we all know it was because Reagan had to compromise with Congress to get them to get on board with his plan and they weren't fiscally conservative) but let's say Reagan's plan was the reason for the increase to the national debt during his presidency - the bailouts and Obama's economic recovery does the same thing - it adds to the national debt, but doesn't even work. Why are democrats happy with Obama's economic "recovery" and telling republicans to be patient and that we shouldn't expect unemployment to go down within two years but Reagan was able to lower unemployment from 10.8% to 7.7% within 17 months because he lowered top marginal individual income tax rates from 70% to 28%, deregulated the energy and banking sectores, and cut deficit spending by 1.5%. This resulted in economic growth, which made businesses flourish, which resulted in a drop in unemployment. More people were working, people who were already working got paid more, which actually increased the income tax revenue to government!. When you couple this with small incremental tax increases, as Reagan did to prevent tax braket creep, the economy boomed, GDP went up, and the national average income went up. Why do democrats think that unemployment CAN'T be lowered within 2 years, when Reagan was clearly able to do what Obama can't?