The last few (seasons 10-12) the show is finally starting to decline, but there's usually at least 1-2 gems per season still
as for someone leaving
Spoiler
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Dennis leaves at the end of the last aired episode cuz Howerton wants to take on other projects. It's unclear whether it's permanent or not but at the very least he's taking a break
S13 was...not so great. Time's Up, Bathroom, and the car episode (sorta) were pretty good, but other than that the season was really weak. Then again the writing's been a bit iffy the past few seasons now. The Super Bowl episodes were probably the worst the show's done
S14 was definitely a return to form imo, obviously didn't hit the same peaks as the show's prime but I enjoyed p much every episode, huge step up from the last couple seasons. Zoo one was prob my favorite
The finale wasn't the greatest but that ending was perf
first two eps were baaaad, but it got better after that. Ireland episodes were fun, especially the latest one. The 'breakup' scene between Charlie and Frank had me laughing the most, their weird dynamic never gets old