If a lens that has basically the same performance as its predecessor can be considered a "dog", then I suppose it is a "dog". It is slightly sharper at some FLs and Avs, it is slightly less sharp at other FLs and Avs.
It may or may not be such an indication. It may just be that there wasn't much possibility to improve over the current optical formula without making the lens much more expensive (cough, cough... Nikon AF-S 70-200mm f/2.8E FL VR... cough).
There was apparently a need to upgrade the electronics for the upcoming EOS RF and it was well past time to add the superior anti-reflective coatings (ala the EF 35mm f/1.4 L II) that do significantly reduce lens flare in certain shooting scenarios. If you are a photographer that desires the better flare performance, this is no "minor" upgrade.
Just because something does not show up on a shot of a flat test chart under ideal lighting from a relatively short distance does not mean that it's not there.
Well, unless your only goal is to be able to brag that you own a lens with the best possible performance when shooting a flat test chart under ideal lighting from a relatively short distance.
To be clear, by "dog," I mean a lens that I wouldn't own. I do own the 24-70mm f/2.8L II, and I used to own the 24-105mm f/4L too--and I actually used both. The 24-105mm was for daytime street, travel, and family photos; the 24-70mm f/2.8L II for events, child-portraits, and corporate group shots. The 24-105mm was also very good for studio lighting when I was going back and forth between groups and individuals. But the 24-105mm f/4L IS II was so bad in three or four brand new copies that I gave up on it, very disappointed with the whole focal-length range.
The only reason I had hoped to replace the version 1 was because I sold my 5D III kit which included it, right at the time preorders were out for the version 2. One of the only times I bought before a review. The owner of my former version 1, a friend of mine, is tickled pink with her kit, but I realized with version 2 that Canon had made an uncharacteristically disappointing new version and gave up on it. Reading reviews after the fact, I think many other people who speak frankly are also characterizing it as a "dog."
As for the 70-200mm f/2.8L IS II, I've never had a complaint about the lens flare or cleaning or other coating related issues. And in fact, a very reliable post here by Lens Rentals indicates there isn't much superior about the new coatings, and they might actually wipe off a little too easily now. This, to me, is another good indication that Canon is clearly moving on from quality innovation in the EF lenses.
Yes they have released new lenses in the past two years. A new 35mm f/1.4L was keenly anticipated because version 1 had some serious shortcomings wide-open, shortcomings which were emphasized by Sigma's Art version, to be sure, but which had been a pain for photographers before Sigma showed what could be done.
I would love to be wrong, to have members here laughing about my prediction months ago that EF was, this year, becoming a legacy tech, supported but no longer innovated. I always predicted there would be an adapter for the new mount, one that would be adequate, but I believed that a new FF mirrorless would bring new lenses that would BEGIN to make EF look second-rate. Is there anything in the release of the four new lenses plus the EOS R that makes you believe Canon is not developing RF as its new pro level mount?
As for the 85mm 1.4L IS being a little soft and still having some minor CA annoyance, how can somebody say Canon is concerned about lens size and weight when they have just released massive RF beauties? Look at that 28-70 IS, and, be still my heart, that NEW FREAKING 50MM F/1.2L!