In this age of molecular biology are the time honored cladistics taxonomy concepts used in biology and botany of “Families, species” etc. still useful, or should it be replaced with something else?
They are being replaced, by lots and lots of intermediate levels. The traditional seven levels of classification and quite definitely not enough, so now there are super-classes, super-super-classes, sub-classes, sub-sub-classes, and etc. Likewise, many bacteria and archaea are classified using far fewer levels, for bacteria because it’s so hard to get a handle on how many strains there are, for archaea because so few of them are known that there’s just no need.
Have a browse around tolweb.org to see what I mean.
And inside of the taxonomy, organisms are being moved around all the time, due to new information from molecular biology.
So yes, In My Humble Opinion the system is due for a constant, unending overhaul. And it’s getting it.
“Families” and any other traditional taxonomic group above the species level is not really a cladistic concept, but a Linnaean one. In fact, cladistics in a sense makes the traditional Linnaean hierarchical system obsolete. There are simply not enough Linnaean categories to accomodate all the branching points identified through cladistics. Continued use of the Linnaean categories is more a matter of tradition and convenience for organizing data, than something that reflects cladistic thinking.
Even at the species level, there is a struggle going on between strict cladists, who prefer the Phylogenetic Species Concept (and similar concepts) to the more traditional Biological Species Concept, which is not cladistic. However, it could be argued that evolution at the species level is not strictly cladistic, since lineages not only split but also fuse before the speciation process (as defined by the BSC) is complete, so that using a non-cladistic definition at this level is reasonable.
The old taxonomy has held back study in a number of classes.
Some early scientists would over-speciate their favorite groups for self aggrandizement.
Once written, unique entries are hard to re-combine into actual species.