Along the spectrum from a one-issue party to a multi-issue party, it would seem we also go from clear support or opposition to incertitude. If a party is a one-issue party, it's clear that those who agree with it on the issue and for whom it is a major issue will be on board 100%, while those who don't agree will not give it a second thought.
Once it becomes a multi-issue party, though, then the more issues it attempts to cover, the more the chances of any given voter disagreeing with at least one of its positions. To take some examples, a capitalist homosexual, or socialist intent on exploiting resources to promote economic growth to pay for social programmes, or a free-market environmentalist, or a socialist nationalist in favour of a larger military, or a free-market internationalist, or a free-market pacifist, etc. etc. etc., though all possibly sharing at least one point in common with the NDP, will likely find it difficult to be fully committed to it owing to 'too much baggage' to carry, there always being one policy or other that they can't fully get behind.
Now of course the Libertarian Party would face a similar difficulty in reverse. While there is plenty for one to disagree with (and, of course, to agree with) in the NDP platform, there is not much to agree with (and, of course, to disagree with) in the lack of a platform in the Libertarian Proposal of essentially having government pull out and do nothing. The Libertarians face the challenge of presenting something people can agree with, while the NDP faces the challenge of not presenting something that could simply bring opposition.
All parties face similar problems of course, with the challenge varying depending on where it stands along the political spectrum. But then the question becomes, how diversified ought a party's platform to become, so as to give enough people something to support without giving too many reasons to oppose? And if it means streamlining the party's official position on issues while leaving other issues to candidates or MPs to decide for themselves, then who would decide how narrow or wide the party platform would be, and what issues would be party issues and what issues would be left to the candidates?