It was a genuine question. I'm not a huge fan of Dier either (I'd rather see him at CB than trundling about CM, but I'd still happily see us upgrade him at CB) but without having a solid opinion on Skriniar, not having paid much attention to him and recently when I watched Inter he wasn't playing as much, I've asked others who have seen more of him and they also seem to think he's a bit of a plodder.
If he's not a bit slow, and there's no truth to it, and he's an all round good egg, why do you think he's fallen out of favour with Conte? If there is any truth in it at all, then what's the point of swapping one plodder for another, especially at the cost of a fair chunk of dough or losing Ndombele.
He is certainly not fast, but I have never noticed him being so slow that it was a major negative for him, my main issue with the Skriniar is too slow for Serie A is more about how is popped up so late. Skriniar started in 30 games and was clearly the starter for the majority of the season in which they finished 2nd, he also played the most games for them the season before when they finished 4th and he personally was recognized as a top CB in the world.
The idea that he is now too slow for Serie A seems like BS to fit a narrative around why he was dropped by Conte rather than being fact. I guess it is possible that at 25 he all of a sudden became too slow or that Inter was so good that they were able to carry him for 30+ games and fool many pundits into thinking he was too slow. I believe he fell out of favor with Conte and the too slow narrative became an easy talking point rather than either blaming Conte or looking into it deeper.
As to why he fell out, I have no idea. I will say although I respect the results which are undeniable I find Conte to be as unlikable a coach as there is and often think he makes odd line-up decisions. I think he more than anyone forms opinions on players (good and bad) and seems to stick with them. I also think he is as committed as anyone to his style so if he thinks you don't fit then goodbye (also why I think the Ndombele to Inter rumours are crazy, seems like a terrible fit.)
As for swapping one plodder for another, Skriniar is much more than just a plodder and his skills, especially defensive IQ, are much higher overall than Dier. I think he is also a much better fit with Sanchez, as he can (much like Toby) run the backline and cover for Sanchez allowing Davison to just focus on the simple things.
I noticed you disagreed about Grealish. He's just the dribbly version of Alli and he's one of the laziest cunts with the ball out there, makes Ndombele look like Makalele.
I have my concerns on how Grealish would fit in a more structured side that doesn't allow him the freedom to roam around and dominate the ball like he can for Villa. But we are so desperate for creativity and the ability to break down defenses that at this point I would take that chance on the hope Grealish could play in a structured role and still bring the ability to breakdown a parked bus. If we are losing Ndombele and going with a Winks-PEH MF pair I also think we need players who can do it on their own as they won't get much help from those two and Grealish certainly could do that as well.
I don't think he is the ideal add, in large part because of his price, but with the make up of our squad, the way Jose is likely to play and select line-ups I want to get in as much creativity as we can because we look to be getting no help in the regard from the manager.