There is something wrong with the way the latter two render text or place their title or axis labels by default.

Is it the way it is cause MATLAB is a non-free product and more effort has gone into their plot rendering engine? Or is it just the poor defaults of the FOSS options and my subjective familiarity with MATLAB that is tripping me off?

Just see [4] (Matlab) and compare with [5] (Gnuplot) and [6] (Matplotlib). Whenever I plot something with the latter two, the resulting graph appears to be "ad-hoc" and "falling-apart".

[1] https://www.mathworks.com/products/matlab/plot-gallery.html

[2] http://gnuplot.sourceforge.net/demo/

[3] https://matplotlib.org/stable/gallery/index.html

[4] https://raw.githubusercontent.com/JimHokanson/plotBig_Matlab/master/documentation/jim_blog/speed_mac.png

[5] http://gnuplot.sourceforge.net/demo/simple.1.png

[6] https://matplotlib.org/stable/_images/sphx_glr_cohere_001_2_0x.png