Designing ships for Starfleet that can be eventually recognized as such by fans is an amazingly fluid process. The original series showed only a single Starfleet vessel. What other ships might have looked like, we really don't know. Our guess would have been weaker than if we had seen only a single aircraft from the US Air Force. The only vessels that were officially designed within the next decade, for TAS, were accepted as being Starfleet vessels despite having only similar types of double nacelles (and sometimes a round bridge component on a flat rectangular hull). Insignia were also helpful. The big and little starships designed by Franz Joseph basically dissected Enterprise and added or fattened parts; they were widely accepted by fans. The refit Enterprise in ST:TMP was basically a slicked-up version of the original, but the vessels that appeared in later movies were even more radical, with Excelsior having an enormous head, fat neck, very long and thin nacelles, and a semicircular secondary hull, which was criticized by the SF movie magazine Cinefantastique as resembling a squished toothpaste tube. Reliant and Oberth were even less Enterprise-like but were still accepted as Starfleet vessels. So, vessels are accepted as Starfleet as long as they include a few correct parts: nacelles with lights on front, and a round bridge on top. If you take a potato and put on that stuff, it would become good enough for Starfleet.
On the other hand, designing a ship to become the co-star of a new TV series is a bit different. You can't just take an earlier ship, like the original Enterprise, and slightly modify the parts in size, shape, and texture. The ship has to be recognized as being a different ship when barely and quickly seen. I've often heard designers say that these ships should be as distinctive and simple that they can be drawn by children. It's also a good idea, but not always required, that the ship is an attractive co-star. So, I think some lead ships of TV series were well designed, but some were not.
I think that the present version of Discovery would certainly be recognized as resembling no other lead ship. It has enough parts to be Starfleet, and I have to say I find it kind of attractive. People who are given an attractiveness ranking of 10 might be considered physically perfect, but they usually end up looking just like every other "10." That would be boring for a lead in a TV series. I think above-average attractiveness with a striking difference is better. So far, Discovery is like that for me.
I guess the only real thing of interest is that they think the changes are more in line with what fans like. 
