Asalamu 'likom wa rahmatullahi wa barakatuh
We muslims do not build any kind of idols like egyptians or babylonians, and there is no special building needed to worship Allah that can leave archeological buildings.
Wa Alaikum ALSalam Wa Rahmathullahi WaBarakathuhu.I agree with you.
Simply finding some fire altars in Harappa or Babilonia doesn't make hinduism or other pagan religions oldest.Muslims don't make any altars ,idols,etc.
Before the time these idols started to be made,there existed Islam which didn't worship any idols.
I don't know what will be left as 'archeological evidence'.
We Muslims don't use any physical objects in worshiping the one and only,the unseen God,Allah Almighty.