Not so much for the slowness. In the case of FitNesse (ugh), it's the Wiki -> Java impedance mismatch, and in terms of Selenium, it's the brittleness. Move an element, watch Selenium tests generated by a QA's browser plugin break.
I rather loathe Hibernate these days (JDBI is my favourite atm), and well, Tomcat feels rather legacy. But I guess that's the advantage of 9 years of advances.
> you can use the maven structure and produce maven artifacts with your build but use a different tool (Make, sbt, buildr, ant etc)
Omg, no, sbt is far, far, far, worse. Ditto ant. Not sure if buildr is still a thing? Looks like the last release was 2017. And as for make, how would you even integrate various Maven plugins into it?