You can judge this by looking at logs, or you could compare fire mage toolkit versus the things other casters have. Other classes dont have blink-while-casting, ice floes, ice block, ice barrier, cauterise, so many instant casts I stopped counting on top of strong dots if you suddenly run out of blinks and floes.
Like I said before... got bad gear or legendaries? Start farming mythic+ and stop crying. Skilled mages are definitely pulling their weight and wont lose their raid spots.