It really comes down to how you feel about who is likely to decline versus who is likely to improve from last season, and also whether you think Counsell will be a meaningful upgrade from Ross. For comparison's sake, here's last season's opening day roster (keeping in mind Seiya started the season on the IL).
Assuming Bellinger signs, the Cubs are looking at likely upgrades at 1B (which was a catastrophe from Opening Day onward) and the bullpen compared to 2023. You can also make arguments for improvements at 3B and the rotation in 2024, although you can also make arguments for regression for either (or both).
The only major downgrade this team might have compared to last season's opening day roster would be CF if Bellinger doesn't sign, and even then, plenty of people are predicting PCA having an NLROY season and there's still the possibility Jed signs one of the other Boras FAs.
It's all a matter of perspective, but I can talk myself into predicting 90 wins for this team if I'm willing to be optimistic. I can't say the same for myself for this time last year, when I thought 81 wins was a massive stretch for 2023.