Tuning (at least in our universe, due to the distribution of the prime numbers) is an exercise in tradeoffs. Indian classical music makes a different tradeoff than western classical (or its direct and indirect descendants), which gives it GREATER freedom than western some areas, and less in others.

Its true that Indian music doesn't modulate (~change keys).

If your goal is modulation (~changing keys), than Indian classical is limited. If your goal is amazing perfectly tuned chords, intricate tuning patterns, and complex relationships between the tuning of notes and rhythms, then Indian classical is MUCH freer than a western-style equal temperament scale.

Modulation (changing chords), as a priority, was a choice made in western music in the 1600s. That choice had downsides, in particular western classical lost access to a larger palette of beautiful "edge of consonance" tone and chord coulors.

Analogy: at its extreme Western classical paints complicated rapidly shifting geometric patterns using a tiny set of "sort of meh" slightly-gray primary colors (think: Escher), Indian classical paints colour fields using a vast array of rich colours (think: Rothco).

The holy grail would be complicated shifting geometries, and complicated shifting colours. These turn out to be in direct tension for math reasons. (Can explain more if there's interest, Pythagoras (yeah, that one) thought there was no tension between the two, but he measured wrong, and the roman catholic church actually encoded "there is no tension between the two owing to the power of God" as dogma, which caused no end of pain for pipe organ makers, who directly knew the two were in tension).

Western classical used to use less regularized tunings, even Bach played (and comnposed for, and imo should be played in) a not-fully-modernly-even tuning. These tunings came from the ratios of integers (directly, or prime numbers, indirectly) and while the chords are unfamiliar in a modern context, looooong held notes tended to be very satisfying to listeners in these "ratio of integer" tunings (or integer ratio) tunings.

That's where gregorian chant comes in, if you hit these exact ratio tunings, once your ear is used to it, chords seem to glow so beautifully you could listen to them "forever". The problem is that switching root notes on a fixed-pitch layout like a pipe organ or harsichord keyboard isn't fully regular.... very roughly (and this is wrong, but conveys the idea) "holding a base note, and the note five keys above it" will sound totally different depending on the base note you pick. This comes necessarily from the math.

So you either end up with an almost infinite variety of physical keys..... or you fudge (tamper, temper, temperament) the pipe organ pipes to "split the difference" and share a key between two not-quite-fully-consonant chords rooted at different base notes.

Unfortunately, now all your chords are a little.... fudgey sounding.... so nobody likes to hear them for a loooooong time (the longer you listen, the more clear the mistuning becomes), so you tend to move faster between chords.

In a nutshell, as European music started wanting total freedom to move around, from anywhere to anywhere, and have each 5-note-pair have EXACTLY the same ratio (resulting in our completely regularized modern tuning equal temperament), the chords themselves were less solid, so you move faster and faster. Once the chords aren't quite as nice, you want to move faster and do elaborate patterns, and the cycle fed back on itself until we got where we are today.

Indian classical made the opposite tradeoff, they traded off harmony, and the ability to root harmony at any point in a fixed keyboard, in return they got a larger variety of VERY interesting tonal colors.

I found western classical tuning VERY limiting due to the lack of colour palette (and, personally, very subjective naturally, I don't find increasing the number of colors to 22-edo or whatever to help, its just 22 muddy colours to my ears... I only need a few colours but I want them to be gorgeous lol ;-)