I use a mouse, but if I said I use a tablet would that mean I know how to draw or is it my art you would need to see.
The reason why I asked that is because some people already are convinced only a tablet can make an artist great. But, the truth is any artist can be great using anything they have to work with. If you only have Mario Paint on a Super Nintendo you will do you best with pixel art. Windows Paint The same thing. It is just as much as the program you use as the tool you hold in your hand, so what makes a tablet make you thing professional digital artist.
I guess it will not take long to see there are thousands of great artist that only use a mouse, but after they were really good they decided to use their skills to get good with a tablet. I don't see why not, because they already have a strong desire to keep the standard of art they know look best and how to get it, so the tablet only makes it take longer to get anything done until they get good at using it.
So I'm sure a lot of great artist could tell you the same thing. You don't need a tablet. You have all you need but the skill and experience. When you have that and stay with it art can appear much quicker with a simple thought. Someone on a phone can tell you their idea, and while they are describing it you imagine and draw it just as quick as the imagination can create it.
You can be that fast with a mouse, but that would be at your peak when you know everything that helps make it easier. Your canvas size, what you do first, and second. The order you follow to fill in an area you imagine you would use then draw and trim with almost not need to trim. That helps you work faster. But the most helpful is to have a great idea what everything looks like. You can't draw what you don't know, and sometimes that throws up a block that could lead to an artist block.
So keep your self free to imaging or do everything wrong, because fantasy is creative, and when it is fantasy it don't need to be right, it just needs to look good.
So get a good program and start using your mouse. It will take a while but you can learn th improve faster when you feel free to try anything.