Rankings aren’t really a fair comparison. A better example would be something like “we’re working on a series of 50 new maps that only Rank X players can play on!” In which case that would be stupid if they were making that many maps for that tiny group of players.
Except beating the Hidden Boss DOESN'T give you anything special as a rewards. A single piece of gear that mechanically, can be easily be replaced by another. Beating Octo Expansion's hidden boss really only gives you a small badge and bragging rights. Just as X rank basically is just bragging rights, there's no real mechanical advantage of being on the higher end of a ranking system. Maybe minor point gain differences, but it's mostly bragging rights.
If you aren't game to put your best foot forwards to get some bragging rights, don't complain that you can't get it.
Just as I and
@Dark Sage Walker said earlier, it's kind of like a Kingdom Hearts secret boss, they're not meant to be beaten by any player, they're designed to be beaten by people willing to put in the work. While he brought up Sephiroth, I'd also like to inform you that Sephiroth is actually considered one of the easier secret bosses in the Kingdom Hearts series. Many secret bosses in BBS in particular are significantly more punishing.
Your only counter argument is that you can heal against Sephiroth, which is not a good one. Different games require different mechanics, but either way it isn't like you can't heal in Splatoon 2, it's called running away and waiting for your HP or armor to regen, which can be done during this fight. Not only that, the secret boss in Octo Expansion isn't necessarily some HP sponge where the battle is drawn out, Splatoon 2's mechanics make for quick confrontations, Inner Agent 3 requires the equivalent of 10 Octo Shot hits per phase (given Inner Agent 3 also heals overtime).
I appreciate the sentiment, but no, I gave up on it. Also, I want do want to make one thing clear for you, when I beat a super hard boss there is no thrill of victory or feeling of glory. Only the feeling of "I'm glad my suffering is finally over." Kind of like being stabbed repeatedly and then it finally stops. For me, it's only the relief of it finally being over. Or in this case, realizing that subjecting myself to that punishment wasn't fun and I'm a lot happier after giving up! Like I said, *if* they ever reduce the difficulty of that fight I'll try again, until then, I'm not going anywhere near it.
Then simply put. That's your problem, not the game's. The cycle of trial and conquest is the premise of most video games, both required and optional content. For many, the act of conquering adversity is vindicating. It just seems that you are not the many.
But all things considered, the secret boss is still completely optional content. Even within the context of Octo Expansion.