That WM looks perfectly ripe to me.
I harvested my last Janosik and again it isn't as good as the first fruit which also was the smallest one.
As you say it is rather mildly sweet but crisp and very juicy. I still enjoy eating it .
How has your weather been? Our summer is none to speak of, quite cold with only some hot days and a lot of rain. So I don't want to judge this variety by only one season. Maybe they improve with more heat and sun. I will grow them again next year.
I am still very suprised how easy it was to grow my own WM. Never looked into it before cause I considered WM a fruit for long and hot summer.
Janosik grew in my greenhouse, which worked like a charme. Only real drawback was the difficult pollination. I hand pollinated, but still got only 3 fruit out of 3 plants.
I also grew some Blacktail Mountain outdoor. I lost 2 of 3 plants to high winds (used landscape fabric without some structure to hold on for the plants). The last plant did set a lot of fruit but did so very late. Pollination outdoors worked much better. I did not hand pollinate. The one harvested fruit was quite small (2 kg) but very very good. Maybe the other fruit won't make it to ripeness, cause the plant already looks like drying back. They don't seem to be very long lived....
I will definately grow Blacktail Mountain again next year.
My father is growing some sweet siberian in his greenhouse. He had the same pollination issues as I. It took him until end of juli to get some sets. Now we are waiting for his fruit to ripen.