I don't understand how it will kill them, considering its not going to replace default Infinity.
The issues with mainly donator servers where the main parts of a pack/challenge can be purchased, this not only flies in the face of the whole idea of a given pack but draws in the ritch kids that seem to have more cash than sense, then we end up with an unbalanced open server with them & us, often the "them" crowd do not hang around too long & you can end up with badly built & lagy setups that are chunk loaded but often used very little, that's the player/donator issues.
Next we have a lot of open servers that are only in it for the money, its really amazing how many players will pay large sums of money to buy there way to success, & there are many server ready & willing to take advantage of this, I'll not go into this any more as its one I feel strongly about & feel some others do too, so could get out of hand.
Next we have the servers that actively promote the reviewing of there servers by giving free server cash/perks, this then while not asking for a good review implies in the wording on near all sites that a good review is in the players best interest, this whole thing make the ftb review section a complete farce, as sites that do not actively reward reviewing get left way down the list, I have seen first hand players log on for the first time & ask how they can collect the bounty from the review they just posted, yeah with out even playing on a server at all...
Lastly as you may well have guessed from above the type of servers referring to not invest a lot in hardware & bandwidth, so can often struggle with over crowding, lack or inexperienced staff, & or poor management.
Let me state here that all servers are not as above but in my experience around 80% do suffer from one or all the above, this is only mho but is gleaned from years of play on open/listed/private servers.