1800p was the old arbitrary resolution detractors stated to use to match DLSS 1.0, I wonder what the new suggested resolution will be now.
It wasn't arbitrary. On early versions of DLSS that resolution was a close match for DLSS performance at 4K, and in many cases *did* offer better IQ. Not since Control though.
Lets not pretend DLSS wasn't crap at first. It was. Same with v1.0 RT implementations. But that's kind of to be expected with any new technology. Initial implementations aren't going to tell you exactly how good it can get, and its always worth waiting a while to see where the ceiling might be.
Anyone who really believed reflections at 1080p in Battlefield 5 represented the high end for this, was clearly ignoring how these changes have gone in the past.
Edit: and lets also forget it's not 'free' in the sense that if you have an RTX card, you paid for the silicon that's handling DLSS and in games that don't use DLSS, those tensor cores aren't doing anything.