No one who knows anything about the game has said magblades are the worst, or anywhere close to it, for at least six months. In 2016 they were a bottom tier class, which may be why you've seen bad things about them. Currently they are the top magicka DPS in PVE and have one of the best toolkits for PVP. The class is difficult to master, but well worth the effort.
@Jpk0012 are you referring to where Izaki said magblade is the hardest PVE class? He's not wrong; the skill ceiling for the class is very high. But that's very different from saying they're the worst. They are capable of outperforming every other magicka class in terms of sheer DPS numbers.
I started a magblade as my second main a few months back and really like the class. Great combination of good damage (not top notch, that's reserved for stam, but really good) and great survivability through shields and self-heals. Two of your main damage skills, sap essence and swallow soul, heal you in the process. Add to that the Nightblade stealth and high burst damage, good for things like Thieves Guild and Dark Brotherhood quests.
With some practice, it's easy to get ~30k DPS self-buffed on the skeleton even without BiS gear (I don't have a single Maelstrom weapon yet).
So from my point of view, magblade takes practice, but is definitely worth leveling to 50.