There is no benefit to spending taxpayer money on creating or sustaining personality cults. The same goes for all public art – the current (local) government should not decide on which people to popularise. No significant market failure exists in physical art objects. The government thus does not need to intervene in the market for statues (copying digital art is another matter). Private individuals can put almost any statues and art on their own property as part of free speech.
The materials of which the statues are made could be used for something beneficial instead, like public housing for the poorest members of society. Clearly the government’s goal in erecting statues is to provide circus to the public in order to get re-elected, not to benefit society.
If the influential people whom the statues depict were asked whether the person or the idea matters more, my guess is that almost all would emphasise the idea. Most would ask the resources to be spent on more reasonable things than statues of them.
If the goal of a statue is to signal the importance of the ideas of the person depicted, then there are more efficient ways for this signalling. For example, a scholarship, a charity or a public library in the name of the person.