Scrypt, yes. Outdated not at all, perhaps mature and well supported are more descriptive of the algorithm. Remember "Our aim is to create a relatively stable, user focussed, crypto currency which refines and implements maturing innovations from the crypto currency sector" ... "no hype or gimmicks, just a project which focusses on becoming a stable every day currency".

Rationale from https://github.com/project-bitmark/bitmark/wiki#proof-of-work : """Scrypt. A well balanced proof of work algorithm which is widely supported and for which hardware support is maturing. Large investment has been made by the mining community, and continues to be made. Whilst there are benefits to both Proof of Stake and multiple algorithm approaches, we feel that Scrypt PoW and the balanced coin release schedule which can be achieved with long term block rewards is the most suitable for this long term project. With an abundance of mining hardware available already it should also ensure a healthy network from the start."""

Has scrypt been proven to do the job we require? Yes.
Is scrypt broadly supported? Yes.

We don't want to reinvent the wheel here, rather we want to ensure the wheel is smooth, well oiled, and stable... fit for purpose.

Thanks for your question danny, and please do review and question further, all input is most welcome.