The lack of political will to support their home grown program is frightening.
It might not be a lack of political will but a straightforward lack of resources and ability?
It takes a lot of political will to support programs like the Tejas and Kaveri decade after decade without giving up on them.
They just can't complete a jet fighter (even a light one) and a turbofan with the technical and industrial resources they have.
The problem plaguing the LCA program is the same problem that plagues many, if not most Indian defense acquisition programs: corruption.
Not to say all or even most Indian officials are corrupt or even corruptible when given the opportunity, but there are nonetheless way too many leaders at just about every echelon looking to line their own pockets at India's expense.
As such, money spent tends to end up being money stolen, and little gets accomplished for every rupee expended.
Technically speaking, it's totally and completely possible for India to succeed at developing something comparable to the F-35 (I think they call it the AMCA?), but it just might be more expensive than the F-35 by an order of magnitude factoring in the requisite bribes, inevitable kickbacks, and some occasional outright embezzlement.
To be fair, Indians are a proud people, and given the legacy and history of their civilization, no one should be surprised or necessarily even offended by their nationalism.
Yet this is perhaps also why corruption involving the Indian military is especially ironic given that many of their visibly patriotic officers literally answer their phones with "Jai Hind!" as their greeting.