I think you're missing my point. Everyone thinks their character deserves to be in Smash Isaac is just one of many fan bases who feels their character deserves to be in the game. Honestly, that will never change. As soon as Isaac gets in, a new character will appear that everyone screams "deserves" it. Heck Isaac isn't even the only character now people say deserve it. I honestly see no reason why you have an issue with just Isaac fans saying Isaac deserves to be in Smash when the Bandana Dee crowd says the same, or the Banjo crowd say the same, or the Geno crowd says the same. "X deserves to be in Smash" is just shorthand for "I want this character in Smash.
I understand your point on this. I think my problem stems more from other options typically being met with some negatives and those negatives being accepted. You can typically say Banjo has license issues, that Kirby may not really need another rep, or that Geno is forgotten by most at this point. Even Ridley had his too big or Sakurai said no outlooks. I feel Isaac and Decidueye (for awhile) have been two more so Golden (ha) boys on here that you typically can't say the "series is dead" or "his design could be rather boring with the amount of sword users in already" without it creating conflict as the same with saying "Mimikyu and Lycanroc are pushed more" or "maybe Incineroar has more character to his design" back when Decidueye was the Golden Pokemon.
Golden Sun dropped in sales with every addition to the series and Dark Dawn really flopped in Japan compared to the other entries. It's popularity has always been more Western focused as well. I played Dark Dawn, I didn't think it was awful myself, but it was alright. Nothing too memorable though. Pairing this that the series has been dead for years now, I don't really know how the series could viewed as that huge hole missing in Smash.
While Isaac has "earth power" his design is pretty flat. I greatly prefer his adult design as his other design looks like any typical filler male in RPGs and farming/town sims. I can see the sword burn out, but I mostly oppose more sword users for FE cause I'd love to see them pull out axes, lances, or more magic. But I understand the fear behind more sword users in general, but I honestly don't hold that as the deal end on characters.
But typically I don't feel these points can be said freely as this forum does have a dedicated Isaac fan group. So typically indicating general disinterest or dislike for the character isn't met well. With both Isaac and Decidueye, I got turned off more so by the one way echo chamber outlook on here. I was kind of hoping Isaac would get in (though I really don't want to hear the sun theories were right... like please... it's the sun during daytime) so it'd stop. But you're right, it'd just move onto someone else.
Still one of my original points still stand in my OP. Even though I may generally dislike some characters or the outlooks in regards to them, I wouldn't be upset that badly by any inclusion. Even if I hate Travis and his games, I may like him in Smash. Even though I found the negative outlook on anything not Decidueye annoying, I may think he is cool in Smash and forget those times. Same applies to Isaac. Good for his fans and he could be really cool. I'm just not big on how big he is made out to be.
Haha, on a side note with Takamaru (yes I support that outdated sword user ;P) being deconfirmed and some leak pointing towards Sable Prince, I won't lie I also started supporting another out dated sword user as well since his snake and frog form could be cute and fun. Maybe I should support Isaac in general as well like in the past as yet another outdated sword user.... I think I just got burnt out on how echo'd his support got as it seemed to get hollower. But still, I wish they'd go with adult Isaac even though they will not. His original look is very "Hi, this is your Farm Player John. Please customize him."
