I strongly doubt that a communist system would be ok with everyone not being onboard. It is highly likely that any disagreeing individuals would be classified as bourgeoisie or enemy of the revolution.
If you're gay and can't marry who you want because the majority says so, it doesn't matter if the dictator or your peers told you so.
What makes communism necessarily authoritarian, as compared to capitalism (which can be, but is not necessarily authoritarian), is that communism is a prescriptive ideology. It stipulates outcomes regarding distribution of resources, how hierarchies are manifested or not manifested, economic relationships, etc. Capitalism is an ideology of systems, unconcerned with outcomes. This is why communes can exist in capitalist countries, but private enterprises cannot exist in communist countries.
A state that governs with a communist endstate in mind might still be regarded as communist, even if they use capitalist policies to get there.
Only if the people aren't onboard. The whole idea of communism is with people being onboard (and running soviets, worker councils, etc).
Some not being onboard is OK - communism is about majority rule, not what some person likes or dislikes. In that, it's like any other system. A modern democracy also doesn't care if somebody likes to sell heroin freely, or whether they'd rather have a King.