This is me answering my own question:
What went wrong is that my installation of Matlab 2017a didn't come with the correct files needed for this job. As a result, I downloaded the patch from here:
There were two useful files inside the tiny zip file within a folder called bin. I just had to find the same folder under my Matlab installation folder and copy-paste these two files in there. Just follow the instructions on that page to fix this problem.
I had no previous copies of these two files in my Matlab directory so I didn't have to back anything up. I only had to add these two files to the directory under the Matlab folder bin/Win64/mexopts
This patch helped me fix the problem I was facing in generating MEX files and now my model runs just fine. :)
For other similar patches, please visit https://uk.mathworks.com/matlabcentral/answers/335092-can-i-use-microsoft-visual-studio-2017-with-matlab#answer_262813
Hope this helps someone else too.