Speakers sound too bright.

I had the same experience with the XTi60's and could not mitigate the brightness. Good ribbon tweeters cost money and quality can vary a lot. The ML's are perhaps a bit too much of a bargain.

I found the RAAL tweeters in the Ascend Towers to have a similar footprint and much better performance. I recommend Ascend.

https://ascendacoustics.com/products/elx-tower-pair?variant=40602626916406

You are jumping the gun here. Let them break in

I agree with many here that your room is probably your biggest challenge.  I have the ML Motion 60's, and actually focused the other direction.  I added a pair of small, sealed Subwoofers (SVS SB-2000) and it was the best money I've ever spent on audio.

For everyone pointing at the room, I tend to agree that is a weak link. But the OP has stated that the KEFs didn't exhibit this behavior, so the room and the equipment are the constants in this scenario. Room treatment will certainly help any speaker perform it's best, but that might be the primary issue here.

I would also recommend letting the woofers loosen up through break-in time.  I bought a used set of B&W 805 D4 speakers that were super bright with little low end.  I solved it by adding some wall treatment but mostly by adding in a Schiit Loki Mini equalizer.  Big difference!  Just $149