What is you definition of being oppressed? And what is your definition of 'someone'? I hope you understand that this mentality, of 'us' vs 'them' and the reactionary politics is mostly rooted in our contemporary realities. All too often I see people conflate this with ancient history, which is dangerous when they don't properly even understand the history they are reacting to.
What your post insinuates is that all of India was held hostage by foreign entities, right? But what if I told you that first of all, there was no 'India'. There was a concept of a greater motherland, sure. But in terms of politics and identity there was no such thing. This is India on the eve of the Battle of Panipat. Who is the 'we' here, and moreover, how do you as an individual relate with those people? The actual humans. This is India on the eve of Muhammad ibn Qasim's invasion. When the only experience Hindus had with Muslims was as sea faring merchants.
The reality is, India had been 'united' very few times in its long, long history. And it is currently in one of those periods as the Republic. This is precisely why people makes a big deal about certain historical states. This concept of Hindu nationalism and in a sense 'Hinduism' itself as it exists today, are relatively modern dynamics. They didn't exist as simply as the 'us' vs 'them'. It wasn't that black and white. But the second claim you made is that your false conception of a monolith was being oppressed. So lets look at that.
If your definition of oppression is an absolute monarchy, then I absolutely agree Indians were being oppressed. But understand that this would've been true regardless of the identity of the Monarch. But if you think indigenous Indians were systematically oppressed and held against their willis as some kind of hostage, I want to you consider a few things. Other than of course that 'Indian' wasn't a thing.
You might be shocked to hear that these states actually functioned with the cooperation from the 'native' Indians. None of these states such as the Delhi Sultanate or Mughal Empire could have even existed without cooperation from the locals. No government can exist that long if it doesn't have legitimacy among the people, thats just not how human societies work. So ask yourself: why was that the case? Was it cus everyone who didn't cooperate would just be killed en masse? Refer back to my point on legitimacy. No government can just do that. But it is very telling that some people would rather subscribe to this theory, than that dreaded notion that maybe Islamic governments in India worked because they were good governments. They were functional in a way that 'the people' deemed superior to what ever they had before, until they decided that was no longer the case. That half of human history right there.
They introduced tax reforms, agricultural innovations, and systems of bureaucracy that genuinely made life better for people. Which is why the people accepted them as their rulers. For your average farmer or merchant, what matters more than the politics of the royals is the economics of the dinner table. And just the fact that these nations were able to hold together their domains in stability and growth for decades on end is a testament to that reality. India was flourishing under the peak of Mughal rule. It had the largest economy in the world in fact. This would not even have been possible if the Indians were being brutally oppressed.
Even when the Mughals were overthrown, it wasn't a black and white Muslim vs Hindu type deal. Muslim worked with Shivaji and the Maratha to over throw the Mughals. How does that fit your narrative? I could go on and on, but this is already getting too long.
But just so you get the points:
Don't conflate modern politics with ancient history.
There was no concept of a united (political) India, just a bunch of independent kingdoms.
These kingdoms independently submitted to Muslim rule, in no short part because it was beneficial for the people themselves.
I'll leave you with an informative video. Just food for thought.