When the Buddha sent out that first group of arahant disciples
, he was still physically present on earth. The dhamma-vinaya had just been thoroughly expounded by him, and it would have (still) been consistently grasped amongst different (arahant) individuals. Plus it was a time in India where social and spiritual conditions were ripe for that sort of thing.
But if we just decide to send ourselves out preaching, 1). we are not arahants
, and thus are not
free of defilements unlike the arahants the Buddha first sent out with that exhortation, who were;
2). 2500 years or so on, the dhamma-vinaya is now understood in many different ways, there is no longer the consistency that there was back then; 3). nowdays social and spiritual conditions are not the same as back then. If you just sit in a park somewhere and invite people to come and listen, people will either think you are a charlatan, or the police or council officers will eventually move you on. And if you go from door to door, well which one of us has not been irritated by that, when it was done to us
by Christian missionaries?
Different time, different place. Let's not become like Christians who 'push' their religion onto others. Rather let us be of as much assistance
as possible, making as much effort as possible to make the dhamma available
for people, to explain it properly
if asked about it (so, let's study the suttas thoroughly), and to assist and support
those that can do these things (such as the bhikkhu / bhikkhuni sangha for eg).
That's my take on it, anyway.