So randomish theories and ideas
Contents of dreams determine flavor.
Doremy can edit the dreams to make them taste better.
--
The Geometry and contents of Dreamworld actually changes with the collective subconscious of those interacting with it.
Thus Whenever an Outsider is in Gensokyo It creates minor ripples but once they leave their influence fades. But when something like Sanae and the Moriya entered Gensokyo (and tied to Sumireko's method of entry) creates more ripples so the amount of objects that Doremy can encounter has increased.
This also creates a bit of a residue on other dreams. There may be representations of things that only could exist in the modern world of the Outside. Interestingly enough Marisa's one who shows such contamination and it may still be lingering after her encounter with the wandering dream soul (ref WaHH29) which shifted her dream out, Of course this means Reimu's dreamspace is contaminated by whatever Marisa's dream was at the time.
Doremy herself even mentions the fact of "seeing dreams about school legends" are something Marisa seems to still dream of and with Sumireko's dream that Marisa was dragged into may indicate the stronger ties
If anything it seems that Sumireko's entry by actively disrupting the realm of dreams by busting out her dreamspace is causing a rather unfortunate set of events in dreamworld.
Oddly enough there is comparisons to S.T.A.L.K.E.R. series and
While the parallel events seemed to have been (mostly) contained in Touhou, in S.T.A.L.K.E.R. it became manifest and those who have played it saw what happened in that game. It seems that really while LoLK's endgame was not 'resolving' the incident it may have resulted in a greater disaster than those who were involved in could think of.
No clue if this fully makes sense but it seems to make some sense to me. But it might be my mind connecting random things incorrectly.
