While I do think more characters in this game appear to be viable/ useable than in the past, and it certainly seems more balanced in the past, I don't think I'd just discount the strengths of other characters.You can't complain about OP characters this early. Nothing has developed yet, advanced strategies for countering characters just aren't there yet. All of the above mentioned characters are not overpowered.
Little Mac is THE character to shield-grab. His grab is too short to grab you and he lacks any sort of range, so when they come at you with a Dash attack (which they often do) or a Jolt Haymaker, you shield it then grab them.
Greninja is actually a character that's based on their opponents ability to predict, I think so anyway. All his moves rely on the opponent not reading him and not predicting where he's going or what he's gonna do. So, an opponent who can work out his strategy has the advantage.
Sheik is not OP, she just has very few bad match-ups. She relies on being very fast and applying the pressure, so any character who can do the same to her is putting her at an even match (or even a disadvantage).
I really don't think anyone in the cast is OP, they did a pretty good job of balancing the game. Only complaints I have are Rosaluma and occasionally Duck Hunt.
Duck Hunt has two excellent projectiles, disjointed hitboxes, powerful attacks, an above average recovery, and that incredibly annoying Down Special.
Rosaluma has Luma, as well as having powerful attacks. However, a lot of her attacks are somewhat slow, so that is a weakness.
Little Mac is NOT good. Flatout, he never will be OP because all you have to do is throw him off and hit him with an aerial. I do agree.
As for Shiek and Greninja, discounting their strengths because they have "weaknesses" and claiming the game seems balanced doesn't mean they don't have some serious strengths.
I believe at this point, it is too early to say anything is OP and that there isn't anything that is.
The only thing that is for certain is that Rosaluma, Greninja, Shiek, and ZSS take less effort to accomplish the same amount of work any other characters do, and those are the 4 most people are referring to as the best at a glance (this early in).
After playing 300+ Glory matches, as well as games with friends similarly skilled in the game, I certainly agree with the synopsis of the community.
Also, I DID agree about Greninja at first, but then I played better Greninjas, and he doesn't JUST rely on reads. He has a counter, a good dash and a good grab, a projectile, a good recovery, above average speed, good disjoints and general range, and it appears his priority is also above average from my observations thus far in addition to that pesky shadow sneak.
I mean, granted, he might have a weakspot, yes, but you can't just discount how many options he has that are good in neutral.
In any case, I do not feel like writing up the reasons why Shiek is obviously one of the strongest characters in the game because you can find the reason in a lot of other places. Same goes for ZSS.
As for Rosaluma, she will probably fall off once people figure out how to deal with the puppet mechanic because she is pretty slow.
I think the game IS more balanced, and there will be more viable characters this time around, but that doesn't mean there aren't characters that are DEFINITIVELY better than the rest of the cast. That is just how things go. There are 49 characters, and they all have vastly different tools and ranges and speeds, and it is impossible to balance things perfectly. The nature of different tools is that some are just better than others.
BUT I don't think we will have another Metaknight thank God.