Kind of shocking he's under water now in a forum that is predominantly liberal or to the left of center.
A lot of this is because Obama’s FP legacy looking back was clearly disastrous and people only didn’t think so at the time because his predecessor was George W Bush . His domestic policy legacy is also not that great in hindsight given the bipartisan deals Biden has made in an even more polarized time and his academic style of liberalism has not worked out anywhere near as good as people thought at the time .
I guess the bigger reason for liberals and progressives is that they feel he squandered the first two years by not getting more stuff done. Like the public option in Obamacare, immigration reform and passed a stimulous too small which took the economy longer to recover. His administration also didn't go after bankers. These are indeed weak spots of his presidency, certainly from today's perspective. He also did a poor job in party leadership and presided over catastrophic downballot losses.