I don't know what current ace you're talking about. Indication are clear from here on that Dusk Lycanroc is going to be the ace from here on. In the character profile updates, it was clearly told to have a special eye on the powers of Dusk Lycanroc, which is a flat out indication that it's going to be a very important Pokemon in this saga who is going to get a lot of spotlight in this saga.
And writers are making it have a rivalry with a Legendary calibre Pokemon which is also indicated by Gladion's statements at the end of SM47 when he states that both Dusk Lycanroc and Type:Null have something in common is an indication of a future rivalry between those two Pokemon.
Gladion also seems to have developed a special interest towards Dusk Lycanroc (similarly how Alain also did towards Ash-Greninja), so this is also an indication that Dusk Lycanroc is going to be the main Pokemon whenever Ash battles Gladion. If that happens, honestly nothing can stop Dusk Lycanroc from being the ace.
And it was a specific choice from the writers that Dusk Lycanroc battled a trainer commanded Legendary (which is generally done by aces and Pikachu). And before you say that's because Rowlet and Litten aren't strong enough for that, the writers could have also had Pikachu battle it, but they didn't. And that's also a huge indication of it being the ace.
Yep, I think it's pretty safe to assume that Dusk Lycanroc will be the ace, and remain throughout.
And for what you're assuming that the creators were rubbish. It's specifically indicated to be an antidote/threat to the UB's, so it's definitely on the level of the mighty UB's and it's pretty safe to think that.
Yeah, as if starters with backstories always become the ace..... *cough* Tepig *cough*. Regardless I already stated my reasoning above that indications are clear for Dusk Lycanroc becoming the ace. Sorry but the one's disappointed are going to be you guys.