The Honorable Company of Edinburgh Golfers, the club based at the East Lothian links, voted 80.2% in favor of admitting women
this week, overturning a ballot that ruled against changing its male-only policy last May.
The course was removed from the British Open rota as a result, but reinstated again this week.
"In this day and age, where you've got women that are like the leaders of certain industries and women that are heads of state and not to be able to join a golf course? I mean, it's obscene. It's ridiculous," McIlroy told a news conference ahead of the Arnold Palmer Invitational event in Florida.
"So, they sort of saw sense. I still think that it got to this stage, is horrendous."
The postal ballot returned 498 votes in favor of admitting women members, with 123 votes (19.8%) against.
World No. 3 McIlroy was still aghast that some members voted against updating its policy, and said returning to Muirfield would leave a bad taste in the mouth.
"I just don't get it," added the 27-year-old, who is targeting a career grand slam of all four majors at the Masters early next month.
"So, anyway, we'll go back there for the Open Championship at some point and I won't be having many cups of tea with the members afterwards."
The club told CNN it had "no comment" to make in relation to McIlroy's reaction.
American golfer Stacy Lewis, a two-time major champion on the LPGA Tour, is less concerned with how the club arrived at the decision, just that it did at all.
"Just the fact things are finally changing is really more the issue," she told CNN.
"It's a great thing for kind of catching up with the times. For a prestigious course like Muirfield, they're the type of place that can make a difference with a lot of other courses going forward for women. People are excited about it."
The International Olympic Committee has warned the golf course set to host the Tokyo 2020 Olympic golf tournament it could lose the event
if it does not award women equal playing rights.
Muirfield club captain Henry Fairweather said after announcing the result of Tuesday's vote: "We look forward to welcoming women as members who will enjoy, and benefit, from the great traditions and friendly spirit of this remarkable club."
He added that the waiting list for new members, male or female, was "two to three years, or longer."
The R&A, the organizer of the Open Championship -- the only one of golf's four major events to be held in Britain -- reinstated the course to the tournament rotation, although not before 2021.
Responding to Tuesday's announcement, Scotland's First Minister Nicola Sturgeon tweeted: "Well done, Muirfield -- decision to admit women members emphatic and the right one. Look forward to seeing you host the Open again in future."