I love alternate tops but only if they look good combined with the right pants. There's some teams who should just stick to white/home road/gray only. All the city connects on the other hand, ummm no. Just kill them with fire.
D-Backs - just stick with the black/red/cream color combo. Goes better with their logo and actual name. Turquoise just doesn't fit a desert team.
Braves - the red 'Braves' tops for home and navy 'Atlanta' tops for road just looks right. No argument here.
Orioles - besides the Cardinals, the only team that matches their colors to their real-life mascot perfectly. Get rid of the black tops for Friday games. They would look MUCH better if the letters/numbers had a white outline. But just stick with Saturday orange tops. Probably my favorite alternate jersey in MLB. It's just perfect with the home white pants. Not so much with gray road pants.
BoSox - see Braves description. But those powder blue/yellow tops? Vomit.
White Sox - Idk which is considered their alternate, but either way, any combo of black/white/gray, pinstripes always looks classic and solid.
Cubs - blue tops not great, not bad. Goes good with either white or gray pants.
Reds - can they just go back to the 2000s with the pinstripes and red sleeves? Those were awesome. The current red tops are just so bland.
Guardians - again, see Braves description
Rockies - the purple tops are sharp, but I wish they had one that said "Rockies" across the chest for home games. But it's damn near perfect with the road gray pants
Astros - not much to be said. They're just okay.
Royals - the royal blue 'Kansas City' is definitely the best one here.
Angels - just too much red. Should have flipped the letters/numbers to white fill with the red tops.
Dodgers - this is a tough one. I don't think they should have an alternate because their normal home/away combo is just so classic and perfected.
Marlins - everything about their current regular uniforms suck. Go back to what they're wearing on Fridays at home this season and you have a solid contender for best uniforms in baseball. Turquoise is just so 'Miami'.
Brewers - I have always liked the Brewers uniforms and alternates. They just always look good with their contrasting color combo.
Twins - what do they have, like 7 different alternates? Can't decide which one I like best.
Mets - can't say I like anything about them. I'd rather use anything with their name on it as TP.
A's - if only their ballpark was half as nice as their uniforms. Those green tops are awesome. Definitely up there as one of the best.
Phillies - see Angels description
Pirates - hard not to like these. Everything looks good with that color combo.
Padres - see Astros description
Giants - the black SF jersey to match the hat looks best
Mariners - whoever picks what they wear and how to combine certain tops with pants should be in control of all 30 teams' uniform selection. They always look sharp.
Cardinals - see Dodgers description
Rays - terrible, just terrible. Worst uniforms in baseball
Rangers - stick with red tops/white pants and blue tops/gray pants
Blue Jays - I guess if you like an overload of blue they're okay
Nationals - the red tops with the piping have always been a nice clean look