Someone will be settling. There's no perfect Democrat. There's a lot of Democrats that just don't give a single shit about anything but social equality issues. Then there's Democrats that don't give a shit about anything but the economic policies. Then there's some that just want a Republican for the economy but a democrat socially. Then there's the inverse. Then there's a lot that only care about the environment. Then there's plenty that are all over the place from hawkish to pacifists when it comes to foreign policy.
With Republicans you are getting someone who wants lower taxes, deregulation, and doesn't really want any change socially. You are guaranteed to get something like that on the right no matter who comes out. It's a matter of degrees. Socially you could have a pence who wants to roll us back to the ice age. Fiscally you could have a psycho who wants to let billionaires run wild and wreck havoc on the economy. But you are generally going to get someone in that range.
Someone's going to have to take some sort of back seat on their pet issues on the Democrat side. With Hillary she got killed by an economic populist sentiment, even though she made great strides in selling herself and rebranding herself as someone who would push for more on social issues (which is where she faultered in 08). You can't predict what will be the driving issue either. In 2008 Democrats got a massive break with the economy tanking right before the election and nobody wanting to trust Republicans with it at that time. It changed the whole dynamic of the election. Republicans were convinced running a strong military guy like McCain while in the middle of two wars was the smart call. And it probably would have helped a lot. But then once the economy hit that mattered so much less.
The thing that scares me the most is that the Democrats have had a really bad habit of trying to make everything about Trump, and I can see that messaging not being very compelling. We already saw a campaign that turned into "look how bad Trump is" fail.