Aryan Invasion Theory (AIT)

Some in India have questioned this view, with some even calling it
something invented to justify European imperialism and missionary
activity. Their view was that the Vedas describe the Harappans and
earlier cultures, and that Sanskrit not introduced from outside but
was always spoken in India. From which some go so far as to conclude
that the Indo-European homeland had been northern India.

However, everything I've seen indicates that the "Aryan invasion" was
real, and that the invasion had happened after the collapse of
Harappan society. Is that a reasonable conclusion?

For example, one big bit of evidence is horses, which are rare or
absent in Harappan remains; Harappan seal stamps depict bulls,
crocodiles, tigers, rhinos, elephants, etc. -- but no horses.
However, the Vedas are full of references to horses. Some anti-AIT
advocates have recognized this paradox and have offered an example of
a Harappan seal that seemingly shows a horse, a "horse" that is more
likely a damaged depiction of a bull. This has been called the
Piltdown Horse by some critics of anti-AIT views.