Yeah, I like Sanders a lot, but it's become abundantly clear in the last few months that the man simply does not have the policy expertise nor the temperament to be an effective President. Those who have called him the Ted Cruz of the left have gone much too far, because Bernie does seem to be a genuinely nice guy who cares a lot about the underprivileged and the downtrodden, but when you combine the totally fudged economics of his plans, his lack of foreign policy knowledge in the most global era in human history thus far, his tendency to either minimize or go WAY too far on the subject of race ("white people don't know what it's like to be poor"), the fact that he has spent most of his political career championing "good" causes while minimizing time spent in the muck of governance because of Vermont's ideological weirdness, he is basically the opposite of what you need in a POTUS right now. That he is right about the general trend of the country in the last 30 years - namely, the total rigging of the political system in favor of the moneyed classes and the institutions of which they are in control - does not ameliorate his many flaws as a candidate. When you combine that with the fact that the GOP is going to be RUTHLESS with him if he is the candidate, Bernie is just a bad choice all around.
