I'd also add that the base game focused pretty heavily on Zelda 1 as well, between the bosses, some of the weapon choices, and the initial adventure map itself.
Was more going solely of character roster, but cannot argue this point. Helps that Zelda has a recurring main cast of characters unlike FE.
Zelda is also much less of a character-driven franchise than Fire Emblem, with the 3d games having much more emphasis on characters, and of the available 3d games at the time, Hyrule Warriors initial wiiu launch focused on 3 of the 5
Firstly, you’re giving Zelda a little too much of a pass by completely ignoring the 2D entries. Its equation would be roughly the same if counted. Even going by HW, they ended up including Link’s Awakening and Link Between Worlds eventually. Sad they never fully got around to the GBA and DS entries outside of Toon Zelda and a few weapons.
Otherwise, yeah, this is the biggest hurdle for FE. They couldn’t really just do the main guy of each game as the series is more based around a large cast, plus all the main lords are sword users in a game that needs axes, lances, bows and magic, amongst other varieties. I believe the game has as many unique play styles as Hyrule Warriors did at launch, but double the character count overall if we include clones. Given the circumstances, I think they did fine. Marth’s games definitely got side-stepped in terms of roster and would argue that it was a poor decision to not have two more characters from his game in place of Lynn and Celica, who are the true cameo characters.
Personally, if I were Koie, I would have just created a sequel that added as many newcomers as the base game of the original, with the previous characters returning. Have Three Houses be the headliner/Fates of the title to get normies in, then do the Binding/Blazing and Radiant games. Lynn was already in the first, so that is one character down, plus they could have more slots by not having 2 characters from other games and 3 originals. Then you can DLC additional side characters from those games like 1 did.
Marth barely being a cameo.
His series got two original characters and a clone, about half of what Awakening got. He also took up the last third of the game having an original boss with Gharnef and stage with the World tree. While he definitely could have used at least 3 more characters, it was definitely more than a cameo role.