200-300 hours is incorrect. The normal airframe life of the aircraft is 6000 hours, and the Taiwanese haven't even used most of it. Their aircraft entered service in 1997 in its modernised 2000-5 form, 15 years after ours did, and still have plenty of life left even without needing to upgrade, at least 2000 hours on the oldest jets. Our jets are being upgraded to 11500 hours to last until 2042, so the Taiwanese jets can last until the late 2050s if we upgrade it before 2030. Out of a potential 11500 hours life, they have at best used less than 4000 hours, likely closer to 3000 hours due to the expenses incurred in maintaining them.
You can't compare it to the Mig-21 because it orignally had a service life of just 2500 hours and was extended by 1000-1500 hours.
As for indigenous projects, yeah, it's a good idea to throw money at our own stuff, but we need fighter jets in large numbers, and quickly. The Taiwanese plan to replace their M2000s with new F-16Vs between 2023 and 2026. So that's how quickly we can get the M2000s. Any indigneous project will begin delivery in significant numbers only after 2025, closer to 2026.