It's wild to me how people think about artists whose work they don't even pay for. 2/3 manga you mentioned have known health problems, and I only say 2/3 because I don't know enough about Itagaki.
Togashi can't physically sit up right anymore without pain and has to draw lying on his back, but you think the guy is just lazy and resting on his laurels.
Murata has undisclosed health conditions (speculated to be gut or autoimmune related) and has spoken about his poor mental health and how both have have contributed to making life difficult for his family.
It's obscenely entitled behaviour to think of these individuals as lazy or unmotivated. Rethink this position.