As a general rule, access is not permitted at all, except by operating crew. Access for ATCO's and some others (CAA inspectors etc.) is permitted by prior formal arrangement only, not on an ad-hoc basis.
There is no doubt that some countries and their airlines outside the EU and USA (we won't name them here) may operate different procedures that are less stringent, involving 'Captains' discretion'. Your desire to visit the Flight Deck is understandable, but to present such a policy as being some kind of return to common-sense is absurd.