I find all these complaints are barely worth the discussion. It is easy to criticise food & seating, but for most passengers that's not what they care most on a flight of less than 2 hours and it is often purely down to personal preference. Food is only a little differentiator when there are two almost equal choices. I fly a decent amount of SAS because I think SAS gets the basics right. I value the Go and Plus concept because it keeps Plus prices and low. The most important feature of Plus is in my opinion its flexibility and that you are prioritised for a free seat next to you if the load allows it (for 2+ hour flights).
I personally prefer the cube over some Lufthansa standard (business) meal, but I can understand that others feel the other way round. They are welcome to choose a LH owned carrier if there is choice instead of SK. I personally have been flying an equal amount of LH-group, SAS and also low-cost carriers (for direct flights) intra-europe and I rather care better schedule, flexibility, handling of IROPS and price when buying my ticket than the food concept.