You should look up the definition of monopoly because they are very far from it

They sure are or were Touchstone is a Disney property and Disney did own the other two for a while and released R Rated content. Just Google R rated films released by Disney.

On June 30, 1993, Miramax was purchased for $60 million by The Walt Disney Company, which paved a way for Disney to enter the independent film market. Harvey and Bob Weinstein continued to operate Miramax until they left the company on September 30, 2005.

Dimension Films is an American film production company and independent film distribution label formerly owned by The Walt Disney Studios and The Weinstein Company and now owned by Lantern Capital. It was formerly used as Bob and Harvey Weinstein's label within Miramax Films, to produce and release independent films and genre titles, specifically horror and science fiction films.
The Weinsteins took the Dimension label with them when they separated from Miramax in October 2005 and paired it under their new company, The Weinstein Company. Dimension Films is one of the American "mini-majors", i.e. small to medium independent television and motion picture production studios.

Touchstone Pictures is an American film distribution label of Walt Disney Studios Motion Pictures. Touchstone typically releases films produced or distributed by Walt Disney Studios with more mature themes and darker tones that are targeted to adult audiences, than those released under the studio's main Walt Disney Pictures banner.[1][2] As such, Touchstone is not a distinct business operation, and does not exist as a separate company.[3]
Established on February 15, 1984[4] by then-Disney CEO Ron W. Miller as Touchstone Films, Touchstone operated as an active film production division of Walt Disney Studios during the 1980s through the early 2010s, releasing a majority of the studio's PG-13 and R-rated films. In 2009, Disney entered into a five year, thirty picture distribution deal with DreamWorks Pictures by which DreamWorks' productions would be released through the Touchstone banner.[5][6] Touchstone then distributed DreamWorks' films from 2011 to 2016.

All 3 owned by Disney at one point as I said and all three released R rated content under Disney ownership.