The first RL belongs to Acura's older school of comfortable V6 sedans, prioritizing smoothness, quiet running and simple premium usability over overt sportiness. That makes it appealing today only if the basics were kept right: timing belt, gearbox, cooling system and steering support.
A good RL I should feel supple and unstrained, not floaty, noisy or overheated. Most of the risk sits in age-related neglect rather than in dramatic design flaws, which means the service record and the overall feel of the car matter more than mileage alone.