I'm a bit confused here. People say Portland cement caused deterioration in 5-20 years. Are not modern brick structures built using Portland cement brick walls?

Also, when repointing an older structure that has lime mortar (white, chaulkish) is it permissible to use Portand cement when PAINTING the outside afterwards? Or will the Portland cement destroy the lime mortar around it anyway? I thought perhaps the paint would prevent any moisture issues regardless of mixing lime joints with new, repaired, Portland joints.

I'm not a mason!

Thanks for help!