More realistic than pessimistic. The game is being marketed as a faithful remake with a very similar artstyle and most of the changes shown so far have been minor QoL features whereas the only actual new content shown has been the Hideaways. They're probably not showing much because it's a copy/paste job and they don't have as much new stuff as remakes like HGSS and ORAS had.
I don't see how the content of the game is an obstacle in creating pre-release hype.
It's not like the pre-release coverage of previous remakes was that centered around new content. Most of pre-release stuff was new artworks and presentation of familliar characters, plots and mechanics. Some new changes were highlighted, sure, but they never made a majority of revealed info (maybe ORAS was a bit different because its pre-release coverage was mostly centered around new Mega Evolution forms, but for the rest of remakes this is totally true). Also, the game is marketed at both old players that remember the originals and the new ones that don't (even more so for the latter, I would say), so the fact that the game comprises mostly of ported old features doesn't make that much of a difference for them.
And there is still a plenty of content to be revealed, such as Poketch, Pal Park or GTS - we know that those things are in the game, but they can't work exactly the same due to various technical reasons. There must be some twist to them, just like in the case of Underground.
I think this suspicious silence has more to do with the fact that the game is developed by ILCA, rather than Game Freak, so it's not treated as seriously by Nintendo/TPC authorities as a new GF game would be (I expect Legends Arceus to get more pre-release hype, although it has a little more time for that). Also, some people seem to believe that Nintendo is afraid that too much hype around Pokemon could "cannibalize" Metroid Prime 4 that comes out on October 8th and is heavily marketed as a big release. I don't believe in this theory that much, but who knows what's on their minds. Upcoming weeks will show if get more BDSP/LA news after the release of MP4.