The IAF do the planning. The execution is done by MoD and DRDO. We didn't fail in the planning, it's the execution part that failed. The IAF still wants what they planned more than a decade ago and they haven't changed anything much as of yet. It still remains 200+ MKI, 200+ Rafale and 150 AMCA.
The MKI's production wasn't planned until 2021, it was supposed to end in 2017. And in 2006, the schedule was moved up to 2014 by increasing the production numbers. HAL failed to deliver the numbers necessary. It was a 14-year production run for 140 jets. You know there's a pretty big problem when the line delivers 16 jets a year, but takes 19 years to deliver 140 jets. Is it surprising that the forces question HAL's ability to deliver the LCA in time considering their track record? Even Jaguar, M2000 and Mig-29 upgrades have been delayed. MKI overhaul was also delayed. Furthermore, the MKI was supposed to be upgraded starting in 2010, alongside its first overhaul, but the govt didn't have the money for it, it was all needed for the Rafale contract. It was supposed to have gone the Su-35 way since back then.
LCA went through a number of iterations before they zeroed in on the current designs. In the 80s, the US defence budget was greater than India's GDP, so they obviously had more options. Now that we have such new options, we are also exercising them, for example, getting competitors for HAL and creating competition within the industry even for R&D through the SPM program.
If the LCA and AMCA designs don't work, then they wouldn't get to the FSED phase in the first place. But since the IAF has planned for 4-6 generations of jets in just 3-5 decades, an alternative is always ready, albeit with a delay. Not so with air forces like the US or France who are stuck with 1 or 2 designs and have no choice but to make them work. The F-35 is the best example. If they screw up, they don't have an alternative. This is what's so amazing about the IAF's ability at thinking ahead, there are plenty of alternatives coming up and there's not a single air force with so many choices and with decisions already taken. Their planning has properly covered all bases. Since we can assume FGFA has failed, the alternative still remains Rafales and a quicker induction schedule for AMCA by splitting it into Mk1 and Mk2, and even then there's still some window for the Su-57 to squeeze through. So only the numbers and types have changed. If the US screws up the F-35, they are screwed for the next 2 decades. Similarly, if they screw up NGAD, they got nothing to fall back on, they can only buy more of the old stuff, basically modernised F-35s.
For each individual program at the high end, there is no real fall back strategy. As the IAF has already pointed out a long time ago, there is no plan B for the Rafale. All you can do is get some more of what you already have, which is what the IAF unfortunately did by pushing the MKI numbers up by 80+ more jets when the Rafale and LCA got delayed, or get an alternative at a later date. The IAF never planned to operate this many MKIs, IAF officers, including two air chiefs, have already pointed that out publicly. If AMCA fails, then the IAF will have to chase after whatever's available in the global market, which could either be the Su-57 Mk3 or the F-35 Mk2. So there is a strategy in place for imports, which is the point of the DPP.
Most of the IAF's plans are stuck due to budgetry issues, not technical or bureaucratic issues. The MKI upgrade was cancelled due to not having the money for it. The Rafale contract was not restarted due to money crunch. FGFA didn't go through because of our poor finances. And now, AMCA is yet to start since it's still awaiting funding. Only LCA was stuck due to the incompetence of our industry, this program never lacked resources.
You see, nothing here is the IAF's fault. HAL screwed up MKI production. MoD screwed up MKI overhaul and upgrade contract. ADA screwed up LCA's development. HAL and MoD screwed up MMRCA. MoD and DRDO (along with the Russians themselves) killed FGFA. And now, MoD has delayed AMCA. These are the facts, with reasons covering financial, technical, bureacratic arenas and with a healthy dose of incompetence. But let's blame the IAF 'cause it's easy, when not a single decision is made by them for any of the above. They only do the planning and create QRs (and pretty modest ones at that), and unfortunately fight with what they have.