This is one of those cases where we have to decide what we will believe!
Most of the info and reading we see says PH is VERY important. But then there are many who find it is just not that way. I Keep mostly African cichlids and everyone knows they HAVE to have high PH hard water. WRONG!
As I started to move into planted tanks, I was concerned with PH dropping when I added pressure CO2. I currently have a tank of Africans who have been gradually moved from 7.8 PH down to 6.4 PH over a period of months. They are all fine with this. My current problem is a protomelas that is rowdy when his female is ripe.
I keep the GH/KH high and don't sweat the PH as it goes down as I raise the amount of CO2 . Steady PH is good but at what number seems to matter very little.
If it suits the fish---it suits me!