Wait really? Player spawn should have 3x3 block wide spot where blocks can't be placed. I don't see any reason why they would remove it, since it used to be a feature as long as I can remember. Sounds like a bug if you can place blocks directly where players spawn though.
Anyhow, the reason why I said it's fairly lost game is because your opponent has to kill your team atleast once so that they can spawn trap your team. Trolling/kill farming isn't allowed in situations like this though, and yes that is unfair if they do that. But I'm not sure if Cubecraft can do anything else than punish people who do that. Maybe making the area where blocks can't be placed even bigger than it currently is could work, like 5x5 block wide spot where blocks just disappear. This could become problematic on smaller maps though since there isn't much room to build in your own base either.