If you want to play that game - you don't get to just look at the 5th starter and the RF and say that those guys upgrade those positions. You're not replacing the RF with Robert, you're replacing Adam Engel, who was a .8 fWAR player. You're not replacing your DH with Madrigal, you're replacing your 1.0 fWAR Yolmer Sanchez. You're not replacing your 5th starter with Kopech - right now you're replacing Ivan Nova and his 2.0 fWAR with him. So, from your 70 win team, with the numbers you just quoted, you have added 2.4 fWAR. That does not make you a .500 team.
If you throw in improvement at several more positions - Eloy 2 extra fWAR Cease 2 extra fWAR, Lopez 2 extra fWAR - now you're approaching a possible .500 team, but that's also assuming no one (McCann, Abreu, Anderson) regresses from their 2019 seasons, which is also possible.
That still leaves you a long way to go in free agency.
To look at the math another way, we are at 23.3 fWAR in 2019. Minnesota was at 54.9. With some margin for error, you need to find 30 fWAR. You've added 2.4 from the list you just said. I will give you another 10 fWAR from guys on this roster - extremely optimistic but not impossible. You upgrade the DH spot, 5th starter, and RF to 2 win players - from the numbers above that's 11 additional fWAR counting the -5 fWAR noted above and 6 added by those players directly. That brings the White Sox to a healthy 46.7 fWAR. That is a solid, strong team, but if fWAR translated directly to records (which admittedly it doesn't) - you are 8 games behind the 2019 Twins. Furthermore, the AL Central has, for 50+ fWAR teams going back to the World series winning Royals, so you do need to load up. Cleveland will be back next year, and could be even stronger - they were demolished by injuries this year and their pitching staff has already found new blood.
There is more that can be found elsewhere. Moncada and Giolito could turn into Bregman and Cole. Cease could come out and do a Giolito. You can improve the bullpen. There are ways to get this team to 50 fWAR based on internal development. But this act that this team is somehow a guaranteed world series contender and the setup you just did to find 10 wins - doesn't work the way you want it to.