In case it wasn't a rhetorical question, Crew Dragon does not have an airlock that would allow for a suited astronaut to leave the craft while maintaining atmosphere inside it. Plus, a big thing missing is a manipulator arm, such as Canadarm, which was used to capture the telescope, and essentially make the shuttle and telescope one body.
I always thought it would be interesting if Spacex developed a "dragon utility module". It would launch in Dragon's trunk and consist of a docking port on one end, an airlock on the other, a miniature manipulator arm and a bunch of cargo mounted around the outside. After separating from the second stage the Dragon would flip around and dock to this module, which would give it all the extra bits needed for a mission like servicing the Hubble.
I don't think it does. But what's to stop the whole (limited) crew from suiting up (without MMUs), slowly venting the interior air, doing the EVA, then returning and re-pressurizing the atmosphere from interior tanks? My guess is it's just uncertified for that procedure, not that it's impossible. And there's no recourse if one of the suits fail.
This is how it worked for all of the capsule-based missions— the entire cabin space is the airlock.
Cabins were also much simpler back then there's a lot more to break in a modern capsule compared to Mercury and Apollo. Actual toilets for starters.
There might also be not enough space to move with a full EVA suit - which is a wildly different thing from in-capsule survival suit.