Read arthashastra for administration.
Architecture - gandhara,mathura,nagara and dravida (chola, chalukya, pallava, hoysala ) architecture complete with manuals.temples of halebidu,ajanta ellora,meenakshi,brihadeshwara in thanjavur,khajuraho and martand sun temples,tower of victory,stupas of ashoka,rustfree iron pillars of gupta era,hampi,nalanda and other universities,somnath,jain temples,stepwells of gujarat etc.Recently popularized halebidu hoysala temples are infact unmatched by any architecture in anywhere in india.
For forts go to rajasthan and maharashtra.Kumbhalgarh has the largest walls after the great wall of china.
Indians still wear saree,and dhoti.Trousers(pajamas and salwar) were introduced by sakas not turks.Mughlai cuisine is only 1 variety,it by no means replaced any regional diets.Indian dance and classical music are unique and beautiful.We have our own languages as well,no need to borrow arab or persian language and script like slaves.
Bigger question is what were the safavid,mughal and ottoman empires doing between 1500-1700 when they were at their peak?Why didn't a single scientific invention come out of these empires when they had all the resources in the world?How did they get technologically outcompeted by small european states that subsequently allowed the west to dominate the world?Were they busy just drinking,praying,fighting,eating and having sex?Then they would have to be counted as failures.
India doesnt need any civilizational lesson,its been a civilization from the times the arabs were eating lizards in the desert.Of the original four - egypt,mesopotamia,india and china only the last 2 are left with anything of their original culture.Even though corrupted and damaged .