The design Eaves recycled for the Inquiry cut-and-paste fleet was the top ship here:
This is the original concept (C) that became the "Neptune-class" and then the Inquiry-class. It was originally made for Deep Space 9 and then developed further for STO, and then of course for PIC.
The Springer and the Orla would've been perfect background ships in DS9, First Contact, etc.
New Orleans and Challenger blend a bit more nicely as "modern" whereas the Springfield, Freedom, Niagara, and Cheyenne are clearly somewhere in that transitional step between Ambassador and Galaxy (I'm personally a fan of the idea that Niagara and Freedom were one off prototyping and testing models for Galaxy components then pushed into service). But I agree broadly speaking.
And look at his DSC season 1 ships, which were a hodgepodge of designs most of which do not conform to any specific era, and could have been used as FC ships for all the viewing audience knew.
Again, because they all came out of the Sampson-class, which became the Walker and the Shepard, and then the others were built out of other concepts for the Walker and Shepard.
That being said as SNW S3 has shown, several work fine as pre-TOS designs with cylindrical nacelles. They should have just given them the USS Kelvin Nacelle design.
In the case of the Ross-class it's a bloody ugly new hat...
I have my issues with it but it's miles better than the other "I hate the Enterprise-E" fan-redesigns of the Galaxy-class IMO.
The Ross and Sutherland classes really make no logical sense as 2401 designs. They don't follow the design flow from the Sovereign/Nova/Intrepid/Prometheus etc., because they were just skins for the Galaxy and Nebula classes.
I think the broader problem here is that there's a habit among fans to translate designs back into previous eras (see the Kusanagi/Matsumoto for the Akira, or the Ushaan and Rapier for the Saber, or now the new "TOS Nebula" model). I don't like that for a lot of reasons.
That being said, I think the Ross does a better job of applying Sovereign and Type-11 shuttle design language than a lot of other designs. Most just feel like... oversized, flat Sovereigns, like the Polaris, Excalibur, or Century.
Odyssey actually feels like it takes the Sovereign's language and builds on it for a new era at least.
someone who never saw those ships before would be hard-pressed to determine what era they actually came from
They actually give a pretty nice post-Romulan War, pre-Kelvin vibe IMO.
and some look like ships from the year 2399 docked over Utopia Planitia before it was attacked...
That was in 2385. That being said yes, the 2390s Inquiry lines are apparent in the design.