MLB banned sticky stuff on June 21.
From that date until his last 9 IP of his season in which he totally fell apart, Barnes threw 17 1P and had a 1.15 ERA and a .530 OPSA.
I have no idea if he used sticky stuff ever, or if he continued to after the ban. But his collapse certainly didn’t coincide with the ban like it did for Richards and Perez.
As for his usage and potential over usage, certainly also a potential factor. Especially after the shortened 2020 season.
2021 was a career year for him, but his contract also essentially paid him like Joe Kelly, another pitcher not exactly known for his consistent performance. But as of right now, I’m very hesitant to say his days may be over