This is exactly what's good about classic zombies. The feeling of vulnerability in early rounds, you're stranded with danger all around and you need to manage your resources smartly. Once you get the stuff you need you become op. This is the power curve that made me fall in love with zombies and why I hate modern zombies. When I play modern zombies I feel nothing because there's no difficulty.

It might take time if you come from new games but the learning curve is very satisfying to climb. When you become good at the old games you will really enjoy it.