For me, the bad taste is that Harry and Meghan want to make a career out of all this, talking about deeply personal matters in public.
Harry could have left the BRF and dealt with his shortcomings in private and quietly. Yes, you can speak about your mental health in public and encourage other people to address their problems but you don't need to discuss every detail in podcasts or in high profile interviews.
Your freedom ends when you enter the other people's freedom. To mention other people, like Kate or Charles or the grandparents, what they have done or not done, is trash talking, pure and simple. Even worse, when you do it in order to get money or attention of an audience you want to use for paying for your lifestyle in the long run.
Nobody's family is perfect, especially parents, but in most cases they do their best or have best intentions.
In the long run, it won't end well, I am sure.