True, the IAF frontline units, logistics and training program for future is all already done around the Rafale. Their MRCA basically gave the tender to Rafale and soft committed long ago. They got 36 and lost several so there's already many to replace. They sunk all the initial fortune they had in the budget for Rafale at the expense of Su-30MKI upgrade program. For fighter budget, they basically only had funds for MRCA (100+ fighters) and Tejas modern blocks development and procurement.
Can't exactly switch to Su-57 instead of Rafale or Typhoon now. What do you do with all the logistics and training you've dedicated to Rafale platform which you planned to complete 100+ units of and negotiated for over a decade on the domestication of certain components and manufacturing. You'd have to negotiate the same with the Russians or entire Eurofighter consortium if you were to switch horses. America is out of the question unless you want to act henchman and you've had major fallout with America.
AMCA is a paper project they never had intention to deliver in 2020s. It's kept in the back pocket and studied.
My understanding is Su-57 is 2030s "quarterback" program to beef up whole force. Sort of what F-22 was for USAF before F-35. Like 2 squadrons(54 aq?) of them.
But now they need sq numbers, i.e. basic “meat" problem.
Lo is Tejas mk.1a(ongoing) and hopefully mk.2. Good, but this is LCA, and it's american engines - a risk. Rising fleet, as Bisons are now disinvested. Most urgent, but apparently there's light in a tunnel.
Medium is Rafale, and it's ultimately core of strike capability.
Hi is huge fleet of MKI, which awaits ever delayed MLU and is right now rather below the bar. Upgrade will bring them up to speed as comprehensive universal heavy platforms(fighter/payloads/ew).
*if* everything goes per Indian plans, by 2035s they're probably going to restore some overmatch over Pakistan.