So, according to you, is this enough for the challenge participation ??

For small and less-know authors, like me, sadly that's very diffult and my only chance to get an upvote is by joining these Challenges.

You can always discover other's content and try to engage with them & increase your content audience.

if the Challenge forces me to write only about a specific argument, I have no choice but write only about that, and be silent about what I would really like to write... and imho that's not good, as everyone gives his/her best by writing about what he/she likes!

Again !! NO ONE FORCING YOU to do stop writing, you can write whatever you want. But if you participate in a contest and want to get the reward from that contest host, then you must listen and follow the instructions the host gives you. It's as simple as that.

they aren't interested in a ruleset they don't even understand, while they can be interested in knowing how I'm performing with my collection, or know how much they can earn by playing a brawl, or what they can expect from the release of the next set of cards.

Okk understand but tell me where on this post, you talked about your collection? where you talk about the rewards? Where you talk about the next set release card? You didn't shared any of those you mentioned. so please don't give excuse of those sweet words.

I know other SPL curator will share their thoughts, but just for your information, I am also part of SPL curation team.