On the contrary, it makes a lot more sense to build something in technology you have expertise in than it does to "use the right tool for the job". I'd rather have less tools to maintain at the expense of them being slightly worse fits.
This doesn't always lead to the best decisions -- although by chance it can work out okay -- and it also has the effect of limiting your horizons. Now I can't say one should learn about every single web server out there, but when the choice is between a dedicated web server and a library in a particular programming language, there is really a lot to see on the other side. Rewrite rules and the wide variety of HTTP stats available for logging are both areas where web servers can give us new ideas.
When I was much younger I thought, why learn databases? I can use Java, I know XML. Just open the XML file and add the records. There's XQuery for searching... The historical precursor for "Why not write everything in Go?" is "Why not write everything in Java?".
I think you can know enough about an alternative to decide whether or not its appropriate without conquering its learning curve.
> I think you can know enough about an alternative to decide whether or not its appropriate without conquering its learning curve.
Yeah, but that's not the same thing as using your level of knowledge as the deciding factor.