Why Blizzard shouldn't listen to people with an active subscription when it comes to Classic Servers.
Because those people are not supposed to play on Classic Servers. The plan is to bring people that quit back to play Classic and probably try to move them to play BfA or whatever expansion is current at the time, not to dilute Wow's player base.
Blizzard cash shop is another reason why this is true. They constantly report that the amount of money they make from an average player is constantly growing. To sell mounts, tokens, server transfers etc. is impossible on Classic servers, otherwise it would ruin them. So it's in Blizzard's interest to do everything possible to prevent moving the player base from Live to Classic, but encourage them to move from Classic to Live.