The disciples expected that Christ would "come" as King, with a royal presence, and to remove the Romans and thrown down the corrupt temple, all at the same time and soon! It was a disappointment for them it turned not out that way, but they came to understand we could have an even much better future because of what Jesus had done. Though they also became convinced of the necessity to be prepared for the time that Jesus would return and that each believer could add by his effort of preaching, to bring the time closer.
All Christians are commissioned and obligated to be evangelizers wherever they are, in that they preach the good news to all sorts of men.
Coming closer to the Latter days we should know about the necessity to proclaim the Gospel or to go out to preach the Good News of the coming Kingdom of God, even when we may encounter many who would like to do everything to discourage us and to put us in a bad light.
Always there have been real followers of Jesus who only worshipped his One God, the God of Israel. Many centuries they worked and preached behind closed doors, avoiding persecution and death on the balefire. In fear of the stake for centuries the real followers of God baptised people in their faith, not demanding to be part of one or another church but being part of the Body of Christ.
An invitation to Jehovah's Witnesses who want or did leave the Jehovah's Witnesses organisation. for them there are many other non-trinitarian groups willing to welcome them as brothers and sisters in Christ.
It is striking that there are a lot of people in the world who are opposed to those who worship Jehovah as their only true God. The vast majority of those anti-Jehovah people come from extreme right-wing groups and fundamentalist or very conservative Christian groups.
Often a lot of people do not know to differentiate between Christendom, Christianity, religiosity and even limit religiousness to Christians, forgetting that there are many other religious groups who have all sorts of worship.