There are a wide range of policy tools that the U.S. failed to use with regards to Kashmir and the oppression of Muslims in India, up to and including sanctions. You can disagree on the efficacy of any particular policy tool, but something with economic and/or diplomatic consequences must be done. Academic research has shown that even the threat of sanctions can help. I'm not holding my breath that Trump will do anything to improve the situation. He has a very warm relationship with Modi.
We should not wait for the arc of history to prove strongmen wrong. We owe it to the oppressed peoples of the world to advocate for non-militaristic measures which help reduce or eliminate their oppression. Some self-doubt is healthy, and the West has done a lot of bad things in the past. We can't let that self-doubt paralyze our foreign policy though. The world would devolve into a worse place. Obama misused MLK's belief on the arc of history (bending towards justice) to justify what is increasingly looking like a terrible foreign policy regime (hands off on Russia --->Syrian genocide--->refugees flooding Europe--->alt-right backlash and Brexit--->Crimea --->alt-right worldwide--->widespread election manipulation--->shaky NATO and EU--->hyperventilating Eastern Europe--->emboldened strongmen--->??? But wait, there's more! Do the claims that sanctions can cause WWIII seem hollow now? Is it becoming clear to everyone that Russian imperialism and Iranian imperialism need just as much scrutiny and backlash as Western imperialism?).
On that note, sanctions on Belarus are very limited. Here's the thing with sanctions: sanctions on one bad actor can be dodged if there are other, larger bad actors who aren't being put in their place. However, systematic sanctions, against all major human rights abusers, would be really hard to dodge. That is especially if we give them a well-defined route out of the sanctions regime, where sanctions are gradually relaxed until the abuses are stopped.
“A man dies when he refuses to stand up for that which is right. A man dies when he refuses to stand up for justice. A man dies when he refuses to take a stand for that which is true.” — Dr. Martin Luther King Jr.