The reason for India's rejection of Su-35 fighters has been named

Military Watch Magazine: The republic intends to focus on the Su-57 program and the modernization of the Su-30MKI

India refused to sign a contract for the licensed production of Su-35 generation "4++" fighters due to plans to improve the Su-30MKI and switch to the Su-57 instead of making new purchases. This was reported by Military Watch Magazine.

Su-35
Su-35

The publication's analysts claim that the republic considered the technological difference between the aircraft already in service and the proposed model insufficiently significant to justify major investment.

Although the Su-30MKI was considered one of the most advanced fighters in the world at the time it entered service in 2002, the technological gap between this model and the Su-35 turned out to be insignificant.
Military Watch Magazine

It is assumed that the new agreement on Su-57 deliveries will involve the modernization of existing plants that currently produce the Su-30MKI — the backbone of the Indian Air Force.

Military analyst Stanislav Fedchishin noted that India is making technology transfer the key condition of the contract for Su-57 deliveries.