You're using projections for Bellinger but last year's results for the rotation. To be apples to apples you need to compare the Soto upgrade over Bellinger to the Burnes/Fried upgrade over some combo of Wicks/Brown/Wesneski/Horton.
There's also a very good chance Bellinger opts out, then it's Soto's 6.5 WAR vs. Tauchman’s 1.5.
The general idea is right that we need to compare the new guys to what they're replacing, which is why 10 WAR =/= 10 Wins. However with Soto you're concentrating 6-7 WAR into one roster spot. You're also, because it's a long term contract, paying ~$40M this year for ~$60M in expected production. There's plenty of that with a Burnes as well, but not with guys on 1-2 year deals.
If you want to maximize 2025 wins in FA, Soto is pretty clearly the guy. I'd go as far as to say by an order of magnitude. There are plenty of good offseasons to be had without him, but he's in line for the largest contract ever for a reason.