What is the primary drawback of using constant linear acceleration to simulate gravity?

The fuel mass required by the Tsiolkovsky rocket equation is prohibitively high.

Simulating gravity through constant linear acceleration requires the spacecraft engines to burn fuel continuously to maintain a steady force of 9.8 meters per second squared. The Tsiolkovsky rocket equation reveals that sustaining such acceleration for a long-duration interplanetary journey requires an exponential increase in propellant mass. With existing chemical propulsion, the fuel required would take up nearly all of the ship's capacity, leaving almost no room for essential cargo or the crew themselves, thereby rendering this method impractical with current technology.