If you take a look at how many Execution servers there currently are, it only makes sense that they wanted to remove the gamemode. I don't think they expected the 5% to care about it, and I do hope they allow the gamemode to stay - they could reduce the amount of servers down to perhaps 3 per region instead of removing all of them.

While on the topic of private matches, the reason why they currently require 6 players to start is because every private match has it's own dedicated server and there aren't many private match servers in reserve, if the player requirement was at 1 or 2 instead of 6 then they would need a lot more servers in reserve, and we all know servers aren't free. The current private match system simply supports scrims and tournaments and such, which do definitely require a dedicated server.

Perhaps the way they could make private matches more accessible to casual players is implementing 2 versions of it; keep the current version which requires 6 players and has dedicated servers in reserve for them, and introduce a private match that can be launched with less than 6 players and uses a pier-to-pier system, therefore no extra servers are needed for this and players can practice and mess around all they want. It seems like a logical compromise, there's no reason a group of under 6 players should NEED a dedicated server, and there's no reason to complain about game smoothness if it's a private match where you cannot earn any XP, therefore the pier-to-pier system for smaller private matches shouldn't be an issue.