IIIIIII feel you.
The worst part is the community that'll just eat it up and say "oh yeah duh, it makes total sense that Dark Samus is an echo fighter, wouldn't have it any other way!"
It feels so ****ing revisionist.
Should Dark Samus have had a totally unique moveset and playstyle? Absolutely.
Would that ever happen in the grand scheme of things? No.
Dark Samus's prime time (heh) was Brawl, which started development after Metroid Prime 2 came out in 2004 and was released after Metroid Prime 3, which came out in 2007 (in North America). Those are her only two appearances. Instead, we got Zero Suit Samus. Then in Smash 4, which came out 7 years after Metroid Prime 3, Dark Samus was an Assist Trophy, not a fighter, which is almost a death sentence. To put things in perspective, Golden Sun's last game with Isaac/Matthew was in 2010.
Combine this with virtually no visible support and I considered that Dark Samus would never happen. Ridley had historic support, but not Dark Samus. Geno, Shantae, Ashley, Isaac, Bandana Waddle Dee, Skull Kid, and many others all have way more support.
The fact that Dark Samus became an Echo Fighter over characters like Shadow and other much more popular picks is already a miracle. The fact that she's in after we already got Ridley is a double miracle. The fact that she made it in 11 years after her last appearance with no sort of campaign or anything is an additional miracle. I'm counting my blessings.
Not going to say that people shouldn't want more. I want more, too. But it's important to put things in perspective. It was this or nothing. And "this" is at least a character with a great deal of effort put into her model and animations, more so than many other characters.