Again that's also an opinion. Shouldn't it be up to every player to decide that and enjoy the game their way?
No, I mean the ending was objectively incomplete as delivered. Whatever one thinks of the creative decisions, they shipped an unfinished product, hence the need for a "free DLC" to fill those holes. The reason they called it a DLC (and why it was free) instead of what it actually was--which is a for the time massive, almost 2gb post launch content patch--is mostly just a desperate attempt to spin what was a catastrophic publicity disaster . . . and maybe a little bit of bookkeeping shenanigans.
Even the name of the DLC: "Extended Cut" belies what it actually is. As if it's extra material that was cut for time like in a movie. Which is not how that works; video games don't generally have limited runtimes. Indeed most such games go to great lengths to maximise the amount of time a person will spend playing the game, up to and including artificially padding out content with pointless grind. In games, cut content is typically either because 1) they tried something that didn't work, or 2) they ran out of time/money. As such, that name is clearly an attempt to redirect the narrative and this is a tacit acknowledgment of the underlying issue.
So yes, the assertion that there's "nothing wrong" with ME3's ending is indeed factually inaccurate, and no that is not a matter of opinion, but objective fact.
Even all that is without taking into account that even the creative decisions made for that final act were a direct result of the same thing that caused it's half-arsed execution in the first place; and that was an arbitrarily truncated development time that gutted the game's content and forced them to engage in narrative triage.
Also; you can't have it both ways. A subjective opinion is just that: subjective. You can't have something that subjectively "has nothing wrong with it". It's a nonsense statement. Whether there's something wrong, or something right, those are both objective matters by sheer definition. Words mean things.