The four-time major winner finished a shot behind Tommy Fleetwood after a three-putt bogey from two feet in the final round and a hooked tee shot into the water on the last hole.
He also made a quadruple bogey earlier in the tournament, which marked his 2024 season debut and first outing since the DP World Tour Championship in November.
Asked on Wednesday if last week's narrow miss was a good omen, McIlroy said: "I'd like to think so.
"I haven't played a ton of competitive golf since the Ryder Cup. I only played four rounds in the DP World Tour Championship, and I wouldn't say I was 100 per cent motivated (having already secured the Race to Dubai title the week before).
"I feel like I've had a three-month off-season. You're going to come back and you're going to make some of those mistakes early on. It was good to play an event like last week where you can learn from them and try to put those things right this week.”
"I would have loved to have won last week, but even with all those mistakes I made, the fact that I still had a one-shot lead going down the last, it says to me that my game is in really good shape," he added.
"I hit the ball well. I felt like I putted well for the most part and if I do the same again this week on a golf course that I know really well, I should have a good chance.”
McIlroy beat Patrick Reed by one stroke to win last year's Dubai Desert Classic after a stunning display over the back nine in the final round.
He is now tied with Ernie Els as a three-time winner of the event and can surpass the South African by winning an unprecedented fourth title.
The world number two, a resident in Dubai for nearly four years before moving to Florida, has deep connections with the Desert Classic, his first professional win in 2009.
For most of his career, he has started his season in the UAE, playing first in the Abu Dhabi Championship (which has been moved to November from this year) followed by Dubai.
Despite nine top-5s in Abu Dhabi in 11 starts, he never won the season-opener, but the Desert Classic has been a different story.
"I think I've certainly got a little more time to put into my game. I'm probably a little unburdened with some of the things that I was going through over the past couple of years," said McIlroy.
"I feel like my focus is firmly back on stuff inside the ropes, and that is a really nice feeling.”
The tournament has attracted a stellar field, with McIlroy the highest-ranked player competing.
Also in contention will be reigning British Open champion Brian Harman, Fleetwood, Tyrrell Hatton and Cameron Young, as well as New Zealand's Ryan Fox, Australia's Adam Scott and Poland's Adrian Meronk.
See a different part of the world
Harman, who made a long trip to Dubai after playing two weeks in Hawaii on the PGA Tour, said he was relishing the opportunity to play outside the United States.
"It's been kind of the first opportunity in my career to broaden the horizons a little bit. So, when I got this opportunity, I jumped on it. Really happy to come see a different part of the world," he said.
"I feel okay right now. I tried to stay on the same sort of schedule. I tried to stay up for as long as I could, and I think I'm doing all right. We'll see how it goes, but we are getting there.”
McIlroy is paired with DP World Tour Championship winner Nicolai Hojgaard of Denmark and Scott in Thursday's opening round.