Yes I suppose it is true that in our day the simple gospel message uses many words that may have to be defined in order for your average joe to understand. I shared the gospel with one of my neighbors once and had to explain what 'sin' was for instance. He was a new Canadian but even with those of us who are generational Canadians we must sometimes also define that word since it has been replaced by 'mistakes' or 'moral relativism' etc. 'Sin' is considered to be a very judgemental and self-righteous word these days.
Simply defined, sin is doing something that we know is wrong and knowingly doing it. Who among us can ever deny doing things that wrong on purpose? Now if we can agree on that definition of sin, then we can reclaim that word and use it without being self-righteous.
So the gospel message may be simple but we are lazy and don't want to spend the time defining our terms.