Doug Armstrong has pulled off some trades that you didn't think were possible until they happened. I'm not suggesting maneuvering this particular piece of business will be child's play or that Tarasenko has high value.
What I'm suggesting is that he's pulled a rabbit out of a hat dealing without leverage before and its resulted in huge adds to the Blues core group like Bouwmeester, ROR and most recently Buchnevich. Do not underestimate his ability to leverage assets like Tarasenko, Neighbours, Bolduc and the Blues 2022 1st. He has one critical lineup hole to fill and admittedly it's a big one, but he has the assets to get it done.
If Anaheim won't part with Lindholm then certainly he can turn his attention elsewhere and find at the very least a suitable target that would meet the minimum requirements (heavy D zone starts, play 20+ minutes a night, strong defensively, can play a shut down role with Parayko bumping Scandella to 3rd pair).
If/when he finds that LD the Blues instantly vault back into the serious contender group but obviously for the cap to work the Tarasenko situation has to be resolved first. Exciting time to be a Blues fan in any case.