Flour labeled as Cake flour usually is weak flour: low W value, or less formally "low protein" or "fewer gluten". This is somehow weird, as some cakes will require weak flour, whether others nedd strong flour (for yeasted dough cakes, if they add lots of fat/oil to the dough, if they add lots of sugar, pieces of fruits/nuts, etc).
I specifically don't know whether Maida is strong or weak flour, despite this answer and it's comments.
Wheat plants has been selected for several milleniums to get more productive varieties, and, yes, grains that give stronger flour.
Substitutes as weak flour
Trying to get flour from a more "primitive" variety of wheat, such as spelt, emmer or einkorn. These are expensive where I live, and usually sold as bio, but maybe spelt is easily found in India. As they have not been so "genetically selected", they still have less gluten than today's "normal" flour. They also tend to have more and better taste than "normal" flour.
Another flour with low gluten content is rye. It has a different taste than wheat, but I thing it fits really well with cakes. This grain grows better in colder climates, so I'm not very sure how hard will it be to get it where you live.
Other flours, as rice or corn / maize have no gluten. It means gas bubbles won't be trapped in, and will result in a much too dense crumb. You might search some gluten-free bread tricks to solve this.
Substitutes as strong flour
Any bread flour will probably work. Maybe it won't rise as much and you'll get a crumb with a denser consistency, more similar to a "chewing gum" than a "soft cake". But if you are ok with this, you can go on.
Note(Thank to @Anisha for the suggestion):
Notice that different flours have different absorption, so some readjustment on hydration should probably be made to the original recipe.
It all revolves around gluten and gluten chains.
Cake flour is low protein, and bread flour is high protein, and everything else lies somewhere between. Individual brands have different levels of protein depending on their formulation. That protein, when combined with water, is what makes your stretchy gluten chains, and those are the difference between soft crumbly cake and a french baguette that could serve as a weapon in a pinch.
As with many chemical reactions in cooking, however, you can interfere with the "natural" reactions by means of some clever chemistry. Cornstarch works very simply...Corn just doesn't have any gluten, so you're just "watering down" the gluten content of your flour.
Acid retards gluten formation. Water is critical for gluten formation, unless you use a whole lot of it, in which case it weakens it (a wetter dough will make for a less gluteny final product). Mixing makes more gluten (helps the little proteins make friends with each other), so mix MORE for more gluten, and less for less.
But fat is your friend. Fat waterproofs your flour, and keeps gluten from forming.
Long story short, pick a method you're comfortable with, and stick to it. If you're used to using AP flour, you're going to have some headscratching moments when the cake flour doesn't behave the way you expect it to. On the other hand, cake flour will be more forgiving if you overmix.
Best Answer
You still need some gluten, otherwise the cake will crumble. Any recipe that is gluten free has to use a number of different additives to mimic the structure provided by the gluten. If you just replaced the flour with cornstarch, your cake or pastry would not be able to rise (it would lack the internal structure to "inflate") and likely crumble as soon as you tried to move it.