I agree that there should be no reason to love one but only by hating another. Every single STAR TREK series has its merits... and its flaws. Obviously, everyone will have a favorite, and that's normal and honestly healthy.
Myself, for example. I am sure I have established on many different threads that DS9 is my favorite. But I saw some STAR TREK in reruns before TNG aired, and then TNG premiered... TNG is what made me a Trekkie.
TOS - it set the template. It had adventure, heart, humor. Some great morality plays in there, too.
TNG - while it can be preachy at times, I'm hard pressed to find a finer example of a scifi tv series to help teach and show ethics and morality to children. And frankly a LOT of adults can use these lessons, too. Data was the reason I became a scifi fan, and seeing his journey was a joy. And there were some GREAT episodes here.
DS9 - I think my views have been made clear on many different posts.
VOYAGER - while it did miss the ball on a lot of things, it did embrace adventure and had some really fun and high concept stories, and some surprising and great characters. I always look forward to seeing this crew now and then, and it is part of my all series rewatch.
ENTERPRISE - while the first two seasons had its flaws, which a bunch of things are due to it being a prequel, it got some mojo in season 3. And hiring Manny Coto as a producer and later head writer was the best decision they could have done. Season 3 and 4 turned out some really marvelous episodes, particularly season 4, which was the best TREK season in a few years, with a couple obvious notable episode exceptions.
DISCOVERY - while season 1 had some things I didn't like about it, season 2 was a massive improvement. I think it will end up being a great addition to the franchise.
In short, I see no reason why one can't take the good AND the bad of each show, because with a franchise of over 700 episodes and baker's dozen of movies, there WILL be clunkers.