Well yea if they get another CM matic isn't bad to have at all, UTD maintain a huge squad always, but there are definitely CM available for a club like Man U that would be better than an aging and off form Matic:
You named one in Nainggolan
They could have went in for kessie if they were quicker
Virati could be bought for the right price
Dier wants to leave tottenham
Naby Keita is a top top player for sure he will move he would work great for Man U
They just missed out on tolisso but he was available.
Fabinho is a player I think they are after and perhaps we should have been
Wylan cyprien from nice is a good young CDM,
Could have got N'zonzi
Goretzka from shakle
There are plenty of CM's available to a club like Man U and plenty they missed out on, but maybe Matic works for what they want I see him more of an option than a fixture they will bring in one more for sure if we sell them Matic.
Verratti and Nainngollan are a class above Matic and would improve them more, however with Verratti eyes being set on Barce will he leave for Man U and we all know how hard it has been to tempt Nainngollan to leave Roma.
In my opinion Kessie, Cyprien, Goetza, Dier and Tolliso, fall into the potential to be better than Matic but currently not quite as good, Although I don't see Dier ever reaching the level of Matic this season let alone the Matic of 2 years ago.
Personally wouldn't have minded us going for either of Cyprien, Tolisso or Geotze as I think they complement Kante more than Matic does and would have preferred them over Bakayoko.
N'zonzi isn't near Matic's level and never will be.
Keita and Fabinho have both had excellent years and are a lot more complete than Matic, whilst very expensive would be obtainable, I think RB Leipzig have quote £70m for Keita. However, I do think Matic will suit Jose and Man U current midfield better.
I think Man U are more in need of someone great defensively to sit behind Pogba and Herrara and thats why Jose is after Matic.
I therefore also would throw Idrissa Gueye into the ring but will Everton play ball unlikely.
For me Jose picking up Matic and say Renato Sanchez for midfield would massively improve their squad and I would much rather they picked up someone like Dier or N'Zonzi instead.
Either way there isn't that many options and Matic would improve them and make them a lot more challenging in the League.