That is my problem with most machines. It seems the stitches get skewed as you have noted. Spending that much money on a machine, I guess I expect straight stitches. However, I do understand the point made that as these machines are made to sew out all kinds of decorative stitches, which allows slight motion of the needle for those jogged stitches. From what I have seen, those stitches seem to be normal for machines at this level.
I would suggest a straight stitch only machine as well. I'm glad I read your post. I plan to add a straight stitch only machine in the hopefully near future, but as I am still researching, I have second guessed my decision, wondering if I should be considering a Janome or other model. My first machine was a Janome MC4800, so when I upgraded a number of years ago, I naturally tried Janome machines first. That said, in general I've never been as impressed with the Janome machines I have tried, this being one of the reasons. I will say I recently sewed on a Skyline 7, that one did surprise me. But I digress - I have a machine that has all the fancy stitches, and that machine is more than I want to spend for what I am after.
I want that bigger throat space for FMQing plus the ability of the machine to handle layers (and sometimes just seam intersections that the other machines seem to complain about). Hopefully you can find a source for one in the UK. Both Juki and Brother are very popular here for straight stitch only machines. Beautiful stitches (both straight FMQing). Brother is a little less expensive here.