Depends on your definition. He's sure not what was considered "conservative" a decade or two ago. But he is what is currently labeled "conservative".
The older definition was small government, limited federal power, fiscally conservative, protect the Constitution. The new definition is... something very different.
This hasn't been true for probably over 40 years. Every conservative presidency has resulted in causing more budgetary issues, increasing the power of the feds and chipping away at the constitution. You can look at the actions taken and the budget over the years. Reagan massively blew up the national debt with Reaganomics, George W followed in his wake and so did Trump. The new definition of the GOP is just what happens when the mask fully falls off and they don't feel a need to lie to people.
In the pejorative sense the word has taken on as the wheels have slowly come off the cart for the past several decades, sure. But as far as the lofty ideals outlined by conservative thinkers, an "institutional arsonist" is basically the polar opposite. The conservatives with any principles remaining got labeled "RINO" and sidelined. And that's saying a lot given what had previously passed for principles.
A correct term is "reactionary", as Yarvin outlines in A Gentle Introduction... . Or less awkwardly and more plainly, "fascist".
The older definition was small government, limited federal power, fiscally conservative, protect the Constitution. The new definition is... something very different.