Please replace commend with

[LittleImp]

Counter point, what does it hurt to have a letter grade on completed battle content? It's not like getting a low score means you didn't clear it, it just means you could do it better. What you do from their is your own choice.

This game has largely been built on a reputation based around not having that thing, and the developers have made it very clear that it's not what they want this game to be about for the majority of its audience. You cannot deny this games explosive commercial success among a largely casual audience. I see new players talking about the lack of meters and rating systems being a positive thing daily in my servers Novice Network. So the answer to your question would be, something like this at this point in the games lifecycle would cause a massive outcry, and likely have more of a negative impact impact on SE's bottom line than a positive one. It simply isn't within their interest to do it.

Furthermore, it could give content more longevity in the form of achievements and possible titles and minor cosmetic rewards.

This is already present in content where effort is actually relevant. Ultimate, Savage, PoTD solo, FFLogs etc. There's even speed rankings for dungeons if you're into that.

It's not a matter of people not wanting to be good at a game. It's people not wanting to make an effort to complete a game but still want to tell people they completed it. It's a behavior bleeding over from outside games where increasing numbers of people want more of the things they're responsible for to be handled by someone or something else. RMT and scammers prey on these people.

This is happening because a lot of companies have realized that there's an optimal mix of free stuff and accessibility that draws the widest possible audience to your game and keeps them engaged. This model is very clearly working for this game. If SE stands to make more money pandering to an audience that doesn't want to work super hard, they're going to do it. Casual players outnumber us sweaty folks at the end of the day, and often have deeper wallets.