Why can't I speak Spanish like natives even though I have been learning Spanish from the last 2 years from different institutes?

The idea is how you learn. The number of years and hours you put into it doesn't matter. The way you know it makes a difference.
First, I'd suggest you go for passive learning, listen to conversations and music as much as possible, as without knowing the culture of a language, you will never be a native to it.
Secondly, while you talk, even be it a piece of one lined information, have your phone next to you to record. Play it as soon as you're done. If you sound different to a native, keep improvising as long as you're happy with your sounds.
Choose one accent, don't go with Spanish and south / Latin American accent, fix one and go for it.
Ultimately, even a C2 in Spanish or any language is called a near-native as a native. One needs to live in the country to be one with the language. As Charlemagne said, " to have another language is to possess a second soul."
Don't try to learn a language; try to acquire it.
I hope this helps!

What matters the most is how have you been taught. Also, the methodology plays a vital role.
I have been teaching since 2005 and have been faculty with many reputed colleges and schools. But I always mould myself as per the student's requirements rather than asking students to cop-up with the generic methods.

Hi Priyadarsani,
I understand your query. I want to suggest you please try to speak Spanish with your friends. And watch any Spanish videos or movies with English title to understand better by seeing the titles. There are so many websites available online, so please try to use them. And take any phrases and try to convert them into Spanish without using any translator. Try to spend some extra time to get more knowledge. Listen to some songs and watch videos. Don't get disappointed. Try everything, you will get success, and you will speak like native speakers.
All the best for your practice!

What will really make you fluent with the language is using the language in day-to-day life, speaking with the natives, and watching more content, videos, and movies related to Spanish.

Moreover, what matters is the teaching method that suits you and how you learn rather than the years you have been learning the language.