It's not that fan content is inherently bad, it's just that i don't want to see BL drown in a massive pool of remakes and whatnot.
i don't think it's logically sound to assume this is the norm/will be the norm if it starts; these are all singular cases and there's honestly only so much that you can do with the idea
It's neat to see something referencing another game, but I can't say i approve of someone blatantly saying "i want to make x game." There's no reference, no interesting mechanics, it's just a blatant 1:1 knockoff of the original product, and often something is lost in the transition.
this is also difficult to say objectively. sometimes, the effort of "remaking" the game is entirely because the mechanics are interesting. other times, it's simply because the content is interesting, and this sort of thing is commonly said and done since it's a fairly simple deal: just generate the same content. more often, i seem to see the former in these theoretical scenarios, and that immediately is a worthy endeavour. if you can develop the mechanics you're trying to replicate in the environment of blockland, you have to understand that, even if the content that goes along with those mechanics is lost, the mechanics of blockland and the content generation abilities they provide are the specific and significant gain to be had in replicating something from another game. as you said, there's often something lost. in fact, there's always going to be something lost; you're taking the piece out of its natural environment and context. what you gain is having the desired elements in a new environment which may be able to apply them in new ways with a new audience and a new set of corresponding content and context.