Communities should be welcoming, for sure. But that doesn't mean communities should just blindly allow everything.

The moderators are responsible for first, talking to the community to find out what the community wants the community to be. Then, the mods should be pruning posts that do not fit. Then, anything that fits should be left to the community to upvote or downvote.

source: I've been a mod in various places for more than 25 years.

On the topic: To me, the best format of the joke is the title leading up to the punchline in the expanded text. A Dad Joke should be relatively short - it's not a story. It is the bare minimum to set up the terrible terrible pun that is the punchline. Generally speaking, an image is not a dad joke, it is a meme. It can be funny. It can have a pun. But not all puns are dad jokes.

It is absolutely subjective, but I think the community would be best served by allowing a single format. With possible exceptions - it's up to the mods to interpret what fits and what doesn't.

A case example of an exception, or at least a deviation - and where moderator input can make a difference. I found r/nottheonion abandoned after someone linked to it and wished it was active. I made it active. As I was building it, there was some submission about a cat or cats or something like that. When I saw it, it had a dozen comments, most of which were "Cat." So..... I realized this owuld be funny. I started removing any comment that wasn't "Cat." (or "cat" or "Cat" or similar). Of course that meant removing a few funny comments that weren't "Cat", but it was H I L A R I O U S to open the thread and see nested "cat" comments all the way down. It was a wildly popular post and helped grow the community.

To me, that encapulates what a mod does: Makes decisions on behalf of the community, with the benefit of the community in mind. I removed valid, funny comments - but in doing so, in that thread only - helped create something so much better. And that's the other point: In other threads, I only removed rule-breaking comments (personal attacks, bigotry).

So no matter what the community here agrees on, I hope the mods will help make it happen.

But I hope the community will not allow memes to take over. Let those be posted in another community.