I use the best I can afford and that is the cotton King Tut thread. Pricey but well worth the money as far as I am concerned. I spend a lot of money of money on QS quality fabrics (unless I find it on sale & frequently do) and Quilters Dream batting and do not want a so so thread. Thst is just MVHO.
Many people use all sorts of threads/fabrics with no problems and I see nothing wrong with that. We all have our preferences and that's what makes us all so wonderful and unique! We can/have learned so much from each others experiences.
Just remember NEVER use the glazed handquilting thread in your machine....it will be a disaster.