It certainly suits Elliott and Carvalho. The 8s in the 4-3-3 have a lot asked of them tactically, whereas the 4 keeps it simple. Also allows Fab and Thiago to cover each other. Probably just lacking depth for suitable CMs and LM.
4-4-2 suits pretty much everyone imo
Carvalho and Elliot get way more freedom in their wide mid roles as kind of wide 10's and more room to what they love to do without getting congested with the wide forwards in a 4-3-3 when playing as 8s. They also have a lot more cover behind them with two holding 6s
I also think the double pivot 6 works best for Hendo too as he just has to be strict with his momvements and shape and has way less freedom so less chance to be caught out
Jota also can play all 4 roles across the front as hes a great 10 so does well in the wide roles and can play the deeper forward or just play and out and striker if needed
Salah is deployed best around the box and was way to wide in the new 4-3-3 they were trying to wasnt much of a threat where as before in the old 4-3-3 it was more of a diamond 4-4-2 when attacking with bobby dropping deep and Mane ans Salah isolated against the Fullback or Centre backs in their channel
Fabinho and Thiago both operate best in a double pivot too and Nunez gets the freedom to float like he likes in his role too and then of course Bobby used to be a 10 and basically gets to play that in this role without having to worry about constantly vacating the box because his other forward is there.
I also think Diaz will thrive in this role too where he gets way more room to do what he likes as he already likes to receive the ball deep
I just dont know how you go back to the 4-3-3 with the players we have