Hot take: people always say rock and ground should be combined but really, it's rock and steel that should be combined into a type
>they are functionally really similar, both dense, heavy, hard, physically defensive material you dig out of the earth
>both are pretty boring honestly, combining them makes that single type more interesting
>rock was steel before steel was steel—it made rock completely obsolete in what it was supposed to be
>both already have a fighting and ground weakness, rock's grass and water weaknesses never made sense anyway
>they also share commonalities in a normal, flying and poison resist, and SE on ice
>doing this makes rock types phenomenally better, while at the same time taking steel down a peg just a little bit.
My biggest issue is that it's hard to find a WORD that combines these two admittedly somewhat different things. The best name I've been able to find for it is the Mineral Type—this covers everything Rock perfectly, the issue is just that Steel is actually an alloy, not a mineral, but IRON is in fact a mineral and Steel probably should've been called Metal Type from the start anyway.