I’d strongly recommend giving this some effort looking into placement and providing some detail on how these are setup in general, amp, use case etc.

Preference is subjective obviously but I find it hard to believe that a portable boomer should perform better than a budget speaker designed by one of the best speaker designers in the industry.

I suspect OP is accustomed to the several dB upper bass hump that those sort of speakers always got.

Check to make sure they're not wired out of phase.

The receiver is set to a surround mode with a center. It’s directing the mids to the center, which isn’t there.

Set it to stereo mode and tell it there are only two speakers.

Show us how your speakers are set up.

I’d venture to guess something is connected wrong. I’ve listened to dozens and dozens of speakers over the years and the Elac B6.2 are fantastic when hooked up correctly to any halfway decent amplifier.

This budget loudspeaker needs pricey, high-quality power to really shine. With your AV, consider moving on.

I borrowed a pair for a year after a living room redo that forced me to part with my floorstanders. I didn t find them too thin, rather neutral in fact, and bass was ok for the size of woofer and cabinet.
My recommendations:

• doublecheck if you speakers are actually in phase (is the + connected to the + of the amp)

• put their backs closer to a wall, that will help.

Depends on size of room too a small bookshelf wont fill up a big room,physics.

First of all: tastes are different, so I would simply recommend getting a different speaker. Life is too short for speakers that you don't like.

However, I am stumbling over your comparison between the Elac B6.2 and your Anker SoundCore Motion. Of course, it is conceivable that you are not a fan of the ~2dB drop at ~1.7kHz, but this deviation is rather marginal and the B6.2 are otherwise quite neutral. In fact, your SoundCore itself has a 2dB drop in the 2kHz range (and other peculiarities in the low treble range).

Even if this may seem cheap, could it be that you simply need to get used to the low end of the B6.2? The Anker only reproduces distortion up to 65Hz, whereas the Elac can reach a good 20Hz lower close to the wall.

My tip would be to place the Elac 50cm away from the rear/side wall and leave the YPAO out for the time being. As the ceiling is rarely damped in modern living rooms, at least a fluffy carpet in front of the speakers would be nice to counteract the dip. Are you sitting in a stereo triangle?

In conclusion: If none of this helps - get rid of it. :D