As you have already read from many of the followers regarding the alternatives. And these are only the best ones.
My suggestion would be to do a research to see which one you find better.
Every software whether its paid or open source have pros and cons.
I am professional vector artist and have worked with many alternatives and have ultimately landed with one final. With my experience I will say to stick with one. Do not over search too many.
Software is just a tool you use, its your designing and creativity that matters the most. I have found that some open source software gives you the same results as a paid one. But yes paid software have many more features.
I would still recommend with Adobe Illustrator(my fav.). But for alternative I would say Mac Affinity seems to be promising.