The modern church is a parody of church. The NT, 1 Cor. 14:26ff, for example is utterly different from the pretend captain of our souls: the pastor/minister/priest. The 'pastor' is a transmogrified priest, that's all. The NT talks about a plurality of service and oversight; not 'leadership and authority'. Yet we resist this at every turn.
Sermons, lectures, would be the poorest of teaching modes. Something like tutorials at uni would offset the largely ceremonial waste of time that a sermon represents. Our church has started to recognise this and we reserve our serious teaching for short courses. Church is not a spectator sport, but in the West has largely descended into that.
Special interest groups?
Be wary of these. I like the idea, but 'social 'justice' groups' (an interest group so biblically bizarre that I had to use quotes within quotes), for example, will usually attract the left side of the church and will go on to interpret everything in the freedom- and soul-destroying doctrines of socialism; often without even knowing it. Such groups must be given instruction that is biblical, and not just cherry picking verses, but grounded in the whole teaching of scripture.
Further, we must remember that political activism can only go so far. An unsaved 'pro-lifer' is as condemned to perdition as a hired killer. So goes for the unsaved solar panel maven, and so on.
Our one core job is to preach the gospel. Not just 'John 3:16-ing people, but...here's an example of a friend's practice:
At his Uni there was a large Muslim forum on Jesus. He went along, ended up having a 90 minute discussion with the mufti. The mufti was much challenged; but my friend knew the Koran and the more prominent hadith. He was well versed in Muslim thinking and culture, he keeps reading and thinking and watching sources that analyse Islam; he keeps rehearsing with every public Muslim he meets his talking points. He keeps track of what was successful, what was rebutted, and improves.
At the same time as this function, the Uni Christian group contented themselves with standing by their tables hoping a Muslim would come along! No! We've got to go there, just as Paul did in Acts 17.
It takes work, study, conversation and endless practice. There's no time for 'social activism'.