She does have a "platform", even if she hasn't based her campaign on a single, narrow issue, in the way that Bernie Sanders did.
You can expect that under a Clinton administration, America will continue to become a more inclusive society, just as it did under Obama. However, Clinton's foreign policy will be more robust, and more aggressive, than Obama's.
It is quite cynical, I think, to refer to Clinton as merely the lesser of two evils -- especially when it comes to policy. It's one thing if you think that both candidates are deceitful. But on some basic principles, the differences are stark.
If you think the three million Muslims living in the US should be catalogued, and those who try to come here should be prevented from doing so, vote for Trump. If, instead, you think America has a responsibility to absorb some number of Syrian refugees, and that American resources should be deployed to vet them, vote for Clinton.
If you think that the 11 million illegal immigrants who currently live here should be deported, vote for Trump. If you think there should be some path for them to obtain citizenship, vote for Hillary.
If you think healthcare should be taken away from the 20 to 25 million people who were able to receive it for the first time after the Affordable Care Act was passed, vote for Trump. Otherwise, vote for Hillary.
In short, Hillary's selling point isn't that she isn't Trump; it's that the country has improved since Obama took office. If you think the country should continue to move in that direction, you should vote for her. If, instead, you disapprove of the country's current trajectory, and would prefer it to be set on new course, directed by an unpredictable, xenophobic braggart who's willing to play fast and loose with our nuclear arsenal, you should vote for Trump.