I feel like someone in design is as annoyed by Mythic Rare power creep as I am, and is actively trying to show it by creating cards directly comparable to Baneslayer and Resplendent angels at lower rarities.
Common and uncommon don't necessarily have to be weaker. (There are, of course, bad rares.) But they will generally be weaker, and common and uncommon play different roles. I would not put dual lands at common unless that was the set's thing, for instance. And the more inherently complex cards cannot be common (but something like Giant Growth or Unsummon, where it has many uses beyond the obvious, can be); cards with an ability that color is not primary in should also be at least uncommon. (This can even apply to P/T: The maximum power for a common creature is 3 for white, 4 for black and red, and no limit for green and blue, but green gets two creatures with power 5 or greater, while blue gets just one.) Finally, if you do a vertical cycle where all the knobs correlate positively (e.g., Bloodfire Dwarf, Bloodfire Kavu, and Bloodfire Colossus), the higher numbers have to be rarer. (Which can of course favor the common and uncommon.) And cards like One with Nothing which have no discernible use at first glance have to be rare.
So to summarize, power is part of it, but there's also complexity, size, color pie, and weirdness.
So to summarize, power is part of it, but there's also complexity, size, color pie, and weirdness.
This is a Baneslayer with +1CMC and -2/-2. I wouldn't say that's someone trying to send a message. It's how commons and uncommons are made.
Jadelight Ranger is a great Rare. Tishana's Wayfinder isn't someone sending a message, it's a common. That's how it's done.