The Wiki article you linked specifically mentions Linezolid isn't necessarily effective against many Gram-negatives (the resistant bacteria): Linezolid has no

The Wiki article you linked specifically mentions Linezolid isn't necessarily effective against many Gram-negatives (the resistant bacteria): Linezolid has no clinically significant effect on most Gram-negative bacteria. Pseudomonas and the Enterobacteriaceae, for instance, are not susceptible.[90] In vitro, it is active against Pasteurella multocida,[2][91] Fusobacterium, Moraxella catarrhalis, Legionella, Bordetella, and Elizabethkingia meningoseptica, and moderately active (having a minimum inhibitory concentration for 90% of strains of 8 mg/L) against Haemophilus influenzae.[87][90] It has also been used to great effect as a second-line treatment for Capnocytophaga infections.[43][92]