TV shows can use whatever design they like and don't have to hold to any era design or style trends if they aren't set in the modern day. A Sci-fi show can do basically whatever and get away with it and historical pieces need to at least look around their eras. For Star Trek, you have this unconformable mix for producers due to it being potentially both sci-fi and historical, where they can do whatever they want, but they already have preexisting designs from the era they are attempting to depict with a large fanbase and non-fan base that would expect things to look at least someone like it did because that's how it looks. If it doesn't look like that it considered wrong and they can't get around that. Even with the 2009 Stark Trek film, things somewhat looked how one would expect things to look based on the fictional time period since the era is established already. The alternate timeline gave them allowances to do changes, but their were still things that looked, more or less the same.
Some of the props shown for Discovery do resemble things from Star Trek with a slightly different take that makes sense given the when it takes place. Other starship designs make sense because our window into Starfleet ships were extremely limited due to ever starship being a Constitution in the 1960s. However because of that, the audience would expect that specific class of ship to look like that still regardless of everything else in the universe. Why? Because that is how that she has always looked for that time period. There is quite literally, no reason to change it. Also no point in changing it. It is what it is, and looks fine from even the ENT era model used for USS Defiant at the end of ENT production era almost 40 years after the ship was designed for this little TV show for NBC called Star Trek. The difference with it being a 40 year old design and a 50 year old design are moot. She is what she is, and can look as good or bad on the screen as you want, but does work all the way up to 4K resolution as a starship.
Some of the props shown for Discovery do resemble things from Star Trek with a slightly different take that makes sense given the when it takes place. Other starship designs make sense because our window into Starfleet ships were extremely limited due to ever starship being a Constitution in the 1960s. However because of that, the audience would expect that specific class of ship to look like that still regardless of everything else in the universe. Why? Because that is how that she has always looked for that time period. There is quite literally, no reason to change it. Also no point in changing it. It is what it is, and looks fine from even the ENT era model used for USS Defiant at the end of ENT production era almost 40 years after the ship was designed for this little TV show for NBC called Star Trek. The difference with it being a 40 year old design and a 50 year old design are moot. She is what she is, and can look as good or bad on the screen as you want, but does work all the way up to 4K resolution as a starship.