My failing ADHD-riddled man-child memory is not to be taken as gospel on any matter, but as best I can recall, they can't reprint Thunderbolt and Smokey because photostrips are retroactively covered by changes to Equity's standard acting contracts made in the decades since, and I think John Wagner has asserted that his renegotiated creative terms with 2000ad retroactively extends to Eagle material as well, so Doomlord is also a no-no.
They are sitting on an anachronistic character forever stuck in a 1950s that doesn't chime well with modern audiences as a setting for a Sci-fi drama.
LOL the Star Wars Sequel Trilogy is on the phone - it says it want to talk to you about retrofuturism as a significant aesthetic movement within the modern creative industries. Holding on line 2 is the cottage industry of period war dramas set in England, and boy does it have an earful for you.
What you call anachronism, others call a selling point. Besides, with the exception of the Wagner/Mills scripts from the first year-and-a-bit of the relaunched Eagle and Garth Ennis' US miniseries, every update of Dan Dare has been a complete disaster. Leaving aside the 2000ad reboot, Dan Dare was reinvented not once but
six times between 1982 and 1989 in the New Eagle* and it sucked ass pretty bad every time.
* "Grandson of the original" Dare, "Star Trek" Dare, "Back-From-The-Dead Space Marshall" Dare, "Gritty Loner with a talking gun who hangs out with Vampirella and Johnny Five from Short Circuit and fights space bats" Dare (this is considerably less awesome than it sounds), "Fugitive Buck Rogers In The 25th Century fighting snake men on the werewolf prison planet" Dare, and finally back to "1950s original and best" Dare in the comic's final years, a retrospectively-bizarre creative choice given that this version would have been out of print more than a decade before the New Eagle's target audience of 8-13 year-old boys were even born, and a full decade-and-a-half before post-ironic nostalgia became a viable marketing strategy.