I went for an Ultegra Ultimate AL from the outlet. The Ultimate AL has the same geometry as the top end SLX frames and gets flawless reviews everywhere. The frames are more in line with CAAD10, top end alloy frames, than bog standard ones.
July Cycling Plus had a group test of £2100-2800 Di2 bikes for example, despite being the cheapest bike on test by over £500, it was the lightest on test and the only aluminium. The competitors all being value brands too, Haibike, Boardman SLR, Focus Cayo, Vitus + Cube Agree.
The frame weights are in the ~1200g area. I just couldn’t see any solid reason to take their bottom end carbon frames over the top end alloy frames.