Accomplishments guarantee pushback.

But policy accomplishments don't really help a president much in terms of popularity. LBJ wasn't popular because he signed Medicare or the Civil Rights Act. It works the other way around; he was able to pass those in part because he was popular in 1964-65, thanks to a very strong economy and public goodwill in the wake of the Kennedy assassination. Notably, all his Great Society legislation didn't help him out once the public got annoyed by the Vietnam War; his party lost many seats in 1966 and he chose to resign rather than face the voters' wrath in 1968.

Beyond that, to the extent productivity and popularity may be related today, they may run in the opposite direction. In a polarized political environment, a president's achievements are likely to generate as least as many enemies as friends. Take health care reform, Obama's signature accomplishment. No Democrat could credibly run for president in 2008 (or for many years before that) without health care reform being a top priority. That was the nature of the Democratic coalition for decades. Conversely, the Republican coalition had been organized for decades around preventing Democrats from enacting health care reform. Obama's efforts were bound to produce substantial pushback, just as Clinton's did twenty years ago. The passage of health care reform indeed exacerbated Democratic congressional losses in 2010, and may well have handed Republicans the House of Representatives.

This doesn't mean that it was wrong for Democrats to pass health care reform or for Obama to do any of the things he's recently done. It just means that actually being productive will engender resistance. Obama is unpopular at least in part because he's been effective.