I've never neglected the bad walk numbers.
OPS has been proven to be one of the most accurate stats at estimating run creation for hitters and prevention for pitchers.
ERA, SIERA, ERA+ and ERA- measure runs allowed and adjusted runs allowed. They ate not projecting run prevention.
Maybe our big issue is over terminology and definitions.
Maybe to you, "very good" is "great" to me, and good is very good. Average is good....
I have used OPS to an extreme over the last few years. To me, it shows a lot. It factors walks and getting on base and also power.
ERA depends heavily on park dimensions, team defense and strength of opponent. While WHIP does capture much of what goes into run prevention, a walk is = to a hit and a single is = to a HR.
You can choose to ignore OPS and OPS Against, but that stat shows Barnes has been much better than Average. Whether it's good or very good might be based on how we define those terms.
If you go by ERA+. Barnes was 27% better than average from 2017-2020 combined. You never answered if you thought that was just good or "very good." I don't like that stat for RP'ers, but I'm using it because ERA is what you seem to like.
You chose to use SIERA, FIP and xFIP to bash Barnes' 2020 season and also said he was "never very good," well, let's look at your chosen stats and Barnes from 2017-2020. Out of 218 RP'ers with 100+ IP, here's how Barnes ranked in those three stats:
SIERA
32nd at 3.21 (That is top 15% and it includes his off 2020 season)
xFIP
15th at 3.12 (That's top 7% or nearing elite status with your stat!)
FIP
(BTW, I prefer xFIP- over xFIP for the same reasons I prefer ERA- or ERA+ and even SIERA over plain ole ERA.)
Ok, say he was not good in 2020, but don't say he was "never" very good. I'll take out 2020 and now tell me, he was never "very good" from 2017-2019:
225 RP'ers with 90+ IP:
29th in SIERA (3.12) top 13%
13th in xFIP (3.02) top 6% and better than Kenley Jackson, Brad Hand and many others.
31st in FIP (3.12) top 13%
I'm not all that big on FIP, but it does have value.
xFIP- has him ranked 13th,also. That is close to elite, and IMO "very good" by any way you slice and dice it.
Really, only BB/9 and WHIP show him not to be very good from 2017-2019. Even here, he is above average.