MATLAB R2019b installation requires supported compilers

I am struggling with MATLAB installation. At the last step, it shows the following message:

However, I have the .net and gcc compilers on my system. It is odd that it also requires MATLAB compiler. Because it should be installed with the software itself automatically. I have never faced such problems when installing earlier versions of MATLAB.

You don't face a problem at all. The installation runs smoothly and MATLAB will work perfectly. Only if you want to translate MATLAB code to C code with the Matlab Coder toolbox, you require a C compiler (such as gcc or MinGW). This is obvious. Why should MATLAB ship a C compiler if there are plenty of open-source compilers (of which you maybe have a preference?) and there is no need for MATLAB (the main product) to run it?

With Simulink it is a bit less obvious but the argument is the same (why should MATLAB ship a C compiler?). Simulink is a model-simulation tool, calling a once-defined model over and over again at fixed (or dynamic) time steps. To speed up the calculation, it actually compiles the code first (note that MATLAB mainly uses a just-in-time-compiler). Those are .mex files, which is basically compiled C code (similar to a DLL). For this, it needs a C compiler and which brings us again back to the argument of why to ship one.

To make a long story short: Don't worry. Go ahead, this is not a problem and totally normal. As you said, you already have a C compiler installed (gcc), MATLAB will find it and you will probably not even note it if you start Simulink or the MATLAB Coder.

BTW, MATLAB always had required those compilers. Only the Java runtime is shipped with it since R2013-something because they had a major issue with the Java update back then and the tech support went nuts =P