Hajj practice from time to time was reformed after the revelation of various scriptures since Prophet Abraham. It is a practice initiated from the period of Prophet Abraham & still be continued. In mid era, This practice was abrogated or lost, but Quran reformed it & made it in place again.
So, is that Hajj practice still in situ or is it lost? Or only some remnants remained?
In this sense, Ancient Hajj practice is still in right place & performed by muslims from around the world.
Also, who's the addressee in 22:27 - and in the mankind, doesn't Jews & Christians included? If so, how do you reconcile with 5:48 that they're to keep their shariyat meaning keep their Hajj at original sanctuary?
In verse 22:27, Quran is addressing only disbelievers. A disbeliever can be from any religion who or what does not believe or support to oneness of GOD. Apart from that, any person who believes in oneness of GOD & follow the provided rules, is a believer. This system is referred to as 'Islam'. In this sense, Any jew or Christian, who believes in oneness of GOD & follows the guidance provided by GOD only, is a Muslim & can perform Hajj. In verse 5:48, Quran is talking about in general word, replacement of previous scriptures with the revelation of the Holy Quran. As I hope you are concerned about previous scriptures being distorted through the pass of many centuries by the human being & that is why GOD himself took responsibility to protect the Quran [15:9] so that noone or nothing can abrogate or distort it. This verse actually is not talking about avoiding jews or christians, but to avoid their distorted thoughts which are already in between them. This is why 'criterion' word is mentioned.