Yes, annoying, but making a big area of the map unreachable towards the rest of the round would break many maps (eg an old city map in EU4 where you spawn in a narrow alley, it would fully block that area of the map).
Plus in some maps, camping the spawn is a good and valid tactic, why would you prevent it? (random plains with a team starting on top of a mountain for example).
Also, it would still not be a fix, they would roam just outside of it and get you as you got out of there, so not a really good suggestion.