Tiafoe, appearing in his third US Open semi-final, was unable to take the final step, falling to eighth seed Shelton 4-6, 6-3, 6-3, 7-5.
Yet his run at Flushing Meadows guaranteed the 28-year-old will climb to a new career-high ranking of world number eight once the post-tournament rankings are released, returning him to the top 10 for the first time since 2023.
"It's been a great season for me, but also, you know, this one is tough," Tiafoe told reporters.
"We wanted to win this one. You know, it's just the last couple of weeks, it's been great weeks, but haven't been able to finish, and that's probably going to be the next thing for me.
"I was doing my interview here last year, and it was really bad how I felt where I was at," he said. "I'm upset, but I'm at the same time so proud of myself of where I've been."
Tiafoe said his ultimate goal, winning a major title, remained unchanged.
"I want to do the thing, man. I want to be a Grand Slam champion one day and just get back to the drawing board and keep working," he said.
The support he receives in New York made another deep run particularly meaningful, but also left him wanting more.
"I just want to win it, man. I mean, the love is incredible. It's something that gives me definitely tears in my eyes from a kid starting how I did, and the love I have here is crazy."
He will now turn his attention to the final stretch of the season and a place at the ATP Finals in Turin, November's season-ending event for the highest-ranked players.
"I'm going to probably feel sorry for myself the next couple of days, but after that, I can start working again and get to Turin," he said.
US Open 2026
The US Open is the fourth and final Grand Slam of the tennis season, running from August 30th to September 13th. It is a hard-court tournament held at Flushing Meadows in New York City. Follow the links below for more information!
All you need to know | Men's singles draw | Women's singles draw | Latest US Open news