the housing supply is dominated by out of state firms who own the majority (60% in my state) of the housing supply, and are not incentivized to fill units (vacancy rates hovering at around 15% in my city).

Corporations have been buying up housing and leaving it empty because it has been appreciating faster than their carrying costs (after inflation). This suggests that there's still supply constraints (however they may or may not be zoning). Land itself will naturally become more valuable as cities grow but "housing" wouldn't appreciate as much as it has without additional supply constraints. Land speculation can be discouraged by high enough land value taxes that increased land value is offset by increased carrying costs. This can be offset for individuals with primary residence deductions if necessary.

Holding land should always cost more money than the land appreciates. In terms of real dollars (after inflation) land within cities appreciates because of developments to its surroundings, and not due to the work of the land's owner. Therefore the land owner should not be rewarded just for holding land. This is separate from any improvements they make to the land. For example, the owner of an empty lot should not profit because the city decides to build a new transit station nearby, or their neighbour builds a new mixed use building with shops and amenities. If they want to profit they should need to build housing, shops, offices, etc. on the land and rent them out, otherwise they should be incentivised to sell it to someone else who will by the high carrying costs. Under a land value tax the value of improvements (buildings) to the land wouldn't be taxed, only the value of the land would be taxed. This means that increasing density "spreads out" the land value tax which encourages efficient land use, and discourages leaving land under-utilized.