There will be a lot of “unfair” or “untrue” comparisons put out here in this thread.
Short answer to your question, no, not even a new 8 or 10 speed gasser with 400+ hp will pull like your LML Duramax. But they will do a great job towing. Folks make too much of this and like to be dramatic. I own or drive a lot of different models of trucks and tow with them and ain’t a hill in WA that a new HD gasser will struggle to get over with your camper.
That said, what are the issues with your Dmax? This is a horrible time to try and buy a new truck and depending what’s up with your Dmax, keeping it could very likely be the best decision.
Emissions? If you got it fixed then roll on. If it’s still an issue, no emissions testing here, I’d delete that sucker yesterday and let er rip!
Something else? How many miles? How has the truck been maintained? What would it cost you to move up to a new truck? All factor in.
If you want to discuss the issues with the Dmax and your current thoughts there, maybe some advice could be beneficial to you with your current truck, if you’re not well read on them.
Cheers!