Why arent they building their own infra/facilities?
Lack of money & will. Never concentrated on domestic development.
Do you know how
sanctions work?
Whenever Indian want to develop sth of its own, immediately some foreign companies jump out and say, "Oh, I can offer you sth advanced than you can develop now." Then, Indian put most of money oringinally for domestic R&D to extreme expensive foreign purchase. And delay their domestic develop program due to lack of money.
Years later, when politics climate changes, and foreigners don't offer Indian these things, Indian realize they should focus on domestic development, but find they lose lots of time & money, getting nothing domestic. It's too late to start development now. So they again beg foreigners to buy things with extreme high prices.
If you're really concentrated enough for years, and lucky to finally develop sth of your own, but with a higher prices due to limited initial production rate, soon foreigners come again, say "I can offer my matured things with cheaper prices. Will you buy?". You're trapped again if you want to buy theirs instead of your domestic ones.
So, if you want to be a real power, never trust foreigners. They're just playing with you, all the time.
When Indian ask for full foreign jets like Rafale or Su-30, they're delivered quickly.
When Indian ask for foreign parts, especially engines, for its own developed jets, they're delayed for years.
Bad actors like US, will take your money and delay delivery for years.
No one will really sell advanced tech aboard. But advanced is relevant of time, so with a delay of 5~10+ years, advanced things can be not that advanced, and can be sold/delivered then. This is how trap works.