I've played it. The issue isn't the kit itself, if there were an entirely new champion there would be far fewer complaints.
The issue is Mordekaiser losing his identity. The master of metal, first of the unliving, doesn't need a babysitter. That's really the crux of the matter. Instead of crafting a healthy new kit for Morde or leaving him alone for the time being, they made the worst decision possible. They forced players to offset his shortcomings be necessitating the presence of a second champion. Sure he functions well in the presence of one of his ghost but that requires taking dragon or successfully killing an opponent.
The gave him strong AD scalings, a need for more HP, reduced his move speed, and eliminated solo split pushing. Not only did they convolute his itemization, they magnified his weaknesses in exchange for an overpowered q that's exacerbated by those very weaknesses as well as a flashy dragon ghost that means he can't use his ult. Morde is incapable of keeping up in a solo lane, before 6, he only has two skills. E which is now essentially shield maintenance instead of damage/harass and Q which is essentially his entire power budget. Morde can't stick to a single target alone without an item that cost 3k gold and doesn't even give any of those fancy new AD scalings. So, anyone with range or mobility doesn't have to engage him. Before the changes his shield and his E allowed for strong pushing mechanics which was Morde's solo niche. Along with being an immobile juggernaut with high burst potential.
Think about this for a second. If Mordekaiser helps his team take dragon, he can't actually ult until the ghost goes away or is killed. Sure he could suicide it under a tower or something but that's really not the point.
The worst part of all this is that these changes will only make things worse for Morde. Either it fails and he's left to be ignored until they can schedule a Sion level rework in a year or two, or it's successful and he's banned out until his numbers are nerfed and he can't cut it bot. The said truth is that there is no healthy way for Morde to exist in bot lane, without people largely abandoning the ADC/Support meta. Honestly before that becomes the norm, he'll just be banned out.
What gets me is that there's such an easy way to manage the new Morde bot. Just focus on his support. Unless it's leona, harassing his support as much as possible makes it difficult for them to stick to Morde to actually activate his shield. Without heavy jungler intervention, Morde is stuck farming under towers in exactly the same predicament many of his lane opponents were previously. So, I guess that's CertainlyT aim here. He deems him too difficult to balance top and is effective removing any possible future success. They may as well disable him until he gets a rework.
At the end of the day, he's either going to get banned or nerfed until he doesn't function well bot and essentially go out the same way Taric did. There really is no way for him to be "healthy" in bot lane.