These mid-tier/B-tier games have never stopped being made. They're just on other platforms.
Can you list 10 out of the last 3 years, not counting exclusives made by first party studios?
Absolutely! They're primarily done by the mid-tier Japanese developers with Sega, Koei Tecmo, and Namco Bandai.
Yakuza 0, Yakuza 6
The Atelier series (all 3 that have been released in the past 3 years)
God Eater 2: Rage Burst
World of Final Fantasy
Star Ocean 5
Tales of Berseria
Nino kuni II
You can really expand the pool by looking into some of the PC only stuff, where Paradox, Creative Assembly, etc. release lots of new games. Also:
Pillars of Eternity
Divinity: Original Sin 2
Of course, some of those you might debate (and I tried to leave some more borderline ones out like Monster Hunter and . Yakuza is close to a higher tier but I've never viewed it as a AAA title. I tried to not include a lot of mid-tier Vita/3DS games from the end of their lives because the list would just be too long. I know there's a lot more out there, I just looked through games I bought.