Most post-"End of Evangelion" Gainax/Trigger shows (including FLCL & TTGL) and about 50% of SHAFT works are strong contenders for my personal "most overrated", but also the majority of popular anime since about 2012

Speaking of which, I've found that most post-2012 SoL/CGDCT shows freaking suck ballz, despite previously being a big fan of teh genre. For one, they're near-universally butt-ugly, seem to ignore that dark shades of color exist, and are painfully low-budget; the VAs are more generic and fake-sounding than ever; and most of them have nowhere near the comedic value, charm, or beauty/tranquility of older SoL shows

/rant