Although the original post makes plenty of sense, I have other thoughts...
People can dream and have those dreams use real life as a basis, meaning that they had a dream that took place in a parallel and fictional version of the universe. The Dream Depot converts that fiction into a "world", meant in the context of "reality", which should be universal in scope based on the logic of the previous sentence, and the logic that I provided in a few previous messages. Obviously, zero characters are literally simulating an entire universe in their dreams, so one could argue that it's possible that, even if a dream is stated to be a universe, a dream world made from it still wouldn't qualify as a universe. However, as the Dream Depot turns fiction into reality and must account for the fictional narrative of dreams of real life taking place within the real life as the dreamers know it, being a universe, it's likely that the dream worlds are universes anyway.
As a counter to the previous paragraph, one could argue that there isn't evidence that the Dream Depot fully converts the dreams of universes into the full universes, and it could instead only convert what's most relevant to the dream. My answer is... Instead of exclusively factoring in the blatantly provided facts, why not look at author intention and the circumstances as a whole? Who except for analyzers like us would give the slightest bother about thinking of the Dream Depot this way? The next paragraph elaborates on this.
The name "Future Dream" implies that the dreamer conceived what the future of their real life would be like, which goes beyond Earth, and "time" beyond Earth in real life, referring to the entire concept of the future rather than a specific net of space-time or just the Earth's rotation relative to the Sun, is on a universal scale. Most people would think of time this way, rather than specifically being on a galactic scale because a dream took place in a galaxy. The Dream Depot already defies most of science, proved that it operates on a cosmic scale, is intended to be a means of wish fulfillment for big dreamers like Mario, as well as being intended to amaze the players of the game with its wonders. Additionally, it's highly likely that the Dream Depot creates separate temporal dimensions for each of the dream worlds, so that one person's potential time manipulation in one dream wouldn't interfere with every other dream. With that being established, I prefer to believe that the creators of
Mario Party 5 didn't go against the fantastical nature of the Dream Depot being only limited by imagination, and that they intended for there to be more than meets the eye at the Dream Depot. I doubt that the creators of the game thought that the reality that is Future Dream ended at being a galaxy just because that's the extent of .
I should clarify that, although it's true that a "world" can mean as little as a biome in the
Super Mario series, in this case, it doesn't refer to a level in a video game, so it's not like the galactic clusters being worlds in the
Super Mario Galaxy games. In most cases, most people don't define "world" as a cluster of stars or a galaxy. It's usually either a planet, a universe, a society, or something political. Technically, by definition of the word "world", the burden on proof is on the downgrade side to prove that there is an unconventional usage of the word "world", being referred to as many stars or galaxies that don't have inhabitants. We know that the dream worlds are beyond planets, so by definition, with there not being societies and politics in the stars, the word "world" likely refers to a universe. I understand that the VS Battles Wiki values statements being specific about this though, so I don't expect this idea to make the biggest difference.
I should clarify that the Dream Depot was also described merely as a land where everyone's dreams come together, which isn't a multiverse. However, with everything I wrote factored in on top of that, the Dream Depot should be a tier Low 2-C structure at the very least. Due to
the way that the Dream Depot was depicted during the credits of Mario Party 5, mixed with how the dream worlds of
Mario & Luigi: Dream Team are treated as separate, it's likely that the Dream Depot is more than just a "land" anyway.