Numerous adjectives can be combined with the. Examples include the poor, the limitless, the miraculous, etc. Such constructions are semantically equivalent to nouns. According to Wikipedia:
A nominalized adjective is an adjective that has undergone nominalization, and is thus used as a noun. In the rich and the poor, the adjectives rich and poor function as nouns denoting people who are rich and poor respectively.
However, it appears that the definite article the can precede adjective phrases as well as single adjectives:
It was a mental hospital for the criminally insane.
It has over the recent years become a playground of the rich and famous.
As always, travel bans do not apply to the rich, famous, or powerful.
If I mistake not, all of these examples possess constructions structurally similar to the poor or the limitless. Therefore, the definite article is combined with the whole adjective phrase (criminally insane/rich and famous/rich, famous, or powerful) rather than a single adjective. Consequently, I think they are nominalizations of adjective phrases rather than nominalizations of single adjectives.