That’s terribly ironic of you to say, since First Past the Post is a contributing factor to why we had two (and only two) poor candidates with a chance of winning.
If another electoral system were used to choose the president, whether it is Approval, Range Voting, or Condorcet, it wouldn’t reduce the incentive to go broad. To the contrary, since it would allow more than two candidates with a real chance of winning, the winning presidential candidate has to be more broadly appealing than two or three or four other candidates, rather than just one.
When it comes to Proportional Representation it’s true you can win seats with a smaller fraction of the vote than FPTP requires, but it would mean that Republicans and Democrats have more competition, so “you must vote for the lesser of two evils” no longer makes sense. You can stop voting entirely for what you percieve as evil (unless somehow all the parties are evil, I guess.)