Travelling during the school summer holidays is always going to create its own issues with passenger congestion and staff stretched in all areas.
I have been a regular traveller from Edinburgh Airport over the last 25 years and its expansion over that period (especially the last ten) has been continual with the builders still resident in the terminal building as it looks to expand further. You could argue that Edinburgh has become a victim of its own success with 11% passenger growth in 2016 and over 330 flights per day. So, despite its continual expansion physically, the terminal building struggles to cope with high passenger numbers but its little different from many other UK airports. My experience at LHR T5, NCL, LGW, LTN, LCY is all the same - a deliberate focus on retail outlets and the associated revenue with actual space for passengers limited and is further restricted by the early formation of queues at gates as passengers anticipate boarding their flights. If you don't have the possibility to use one of the airline lounges, which are relatively quieter, Edinburgh is not a pleasant experience but not that different to other UK airports listed above. The only way to overcome the issues you mention are to improve staffing levels throughout the airport, change the building 'model' to provide more room for customers (no, we don't all want to look around shops) and spend some revenue on the cleanliness and hygiene within the terminal building. Will it happen? Just take a look at the profits Edinburgh Airport is making and draw your own conclusions.