Yes, taste is the most important and I didn't include the subjectivity of taste in the post as a parameter because, in this forum/space, I'm comfortable assuming that piece of knowledge as taken for granted.
Preference and taste are
individual. Every reputable seller I know in Taiwan insists as much as possible that I sit and they pour the tea for me before allowing me to buy, no matter how famous the tea. I've been poured very expensive teas that I did not buy, but the human connection made and the tea knowledge gained are both rich.
For those whom wish to inform themselves I do believe it can make a difference, if one knows the tea, the region, the farm, the varietal, the maker, the weather, the harvest date, etc., not just for what this contributes to one's imagination but also over time one can begin to make informed inferences about the tea they are purchasing. For me it's nice to be connected to the process as much as possible. Not to mention there is also the immense joy, for me, in educating one's self to the depth and reality alive in anything, but specifically tea, gong fu, etc. It's a rich personal process.
So, while knowing the above mentioned list won't necessarily mean I'll enjoy the tea, it still has value. And I have made repeat purchases based on my inferences that have paid off and proved, more or less accurate, luckily
Lastly, one seller I know in Taiwan prefers to follow certain makers, asserting that a great maker/tea master can do immense things with a poorer tea or tea from a difficult year. Rather than having a loyalty to certain farms, this vendor buys from wherever his esteemed makers move to process the harvest, which in this form, throws off the whole farm loyalty/location piece, more or less.