There are two problems:
1. The protocol limits the maximum block size to 1MB (https://github.com/dogecoin/dogecoin/blob/master-1.5/src/mai...) which puts Dogecoin's maximum transactions per second at 70, without a forking protocol change.
2. Dogecoin targets one minute between blocks, which is 10 times faster than Bitcoin's 10 minutes per block. That number wasn't chosen arbitrarily. There needs to be plenty of time for new blocks to flood the network, otherwise forks will become more common as miners work on outdated information. This leads to reduction in effective hashrate and increased centralization of miners. Increasing the maximum block size significantly will be at odds with Dogecoin's faster confirmations.