Are contracts signed using electronic signatures such as NemID legally binding?

Yes, it is just as legally binding and a lot more secure to sign contracts using electronic signatures. Obviously it's also faster.

In reality, you rarely get a contract on paper anymore. Just like parties and lawyers negotiate remotely using phones and emails, contracts are being printed, signed using a pen, scanned and emailed and then a lawyer is merging the different scans at the end of a pdf containing the contract. This silly practise has lasted for many years although it is wrong on so many levels. 

The EIDAS regulation establishes a framework for electronic signatures throughout Europe.