My MSB was a Xmas present and have worn it every day since. I workout 5~6 days/wk and have been on my wrist almost all day, except when charging.
I don't have any of the issues as shown in the images by OP, and I do clean MSB with foam hand soap and water 1~2 times/week by running it under the faucet.
Yes, there are some scratches to the face/frame, and just recently, I've picked up a real scratch to the glass display. I got careless and scraped it on stucco doing yard work, but its hardly noticeable.
My sense is that some people's skin/pH balance causes more damage than others. This is very common amongst leather watch straps. For some, a strap last a very long time, whereas for others only few months. Its all a type of chemical reaction.
It would be a mistake, I believe, to over generalize few examples as a predictable outcome for everyone.
Last, need to set the life duration expectation for fitness bands. If it last 12~18 months (my criteria), then it met its lifespan expectation. I realize OP's Band is only 6 months so there is a problem - I agree. But its only $200, and not $500~$600, like Apple Watch.
I have not been too interested in AW, because I have a watch that I like and has a sentimental value that goes with it. Its a jewelry watch that cost few thousand that we bought on our honeymoon in NZ years ago. That said, when it breaks, I'll probably get whatever generation AW then, with an intension to replace it every 2~3 years, like I do with iPhone.