Not using the STL in and of itself is not terrible advice, it's a trade-off. For example, I tend to avoid the STL because of how inconsistent it is across the various compilers in terms of performance and behavior. The standard leaves a great deal of ambiguity in how the STL behaves and those inconsistencies can be frustrating to deal with when you're writing cross platform software. Furthermore plenty of embedded systems also cut out the STL entirely due to disabling exceptions. Using fast-math is also a perfectly acceptable option for numerous domains that do not need strict IEEE conformance, such as graphics programming or training neural networks.

If people were to listen to your advice, no one would ever post any kind of article on how to achieve certain specific goals, all we'd ever discuss are very generic topics and constantly rehash the same content over and over again. It's good to be able to learn how certain developers manage to accomplish various goals without having someone come along and call that advice terrible.