I have been to Urquhart Castle, and it is still beautiful, though a bit busier. There are still thousands of empty and gorgeous places in Scotland. One place I love is Orkney, which is north of scotland. VERY empty drive there and even ferry ride is nice. There are stone circles 800 years older than Stonehenge on Orkney and you can walk right up and touch them and are very likely to be the only person there! Also check out this 5,300 year old neolithic site. https://www.visitscotland.com/info/see- ... ge-p247671
And more on Orkney: https://www.visitscotland.com/blog/orkn ... of-orkney/
Another of my favorite places in scotland is https://www.islayinfo.com/
One solution to crowded planes is to fly British Air and get their Economy Plus seats, which are the equivalent of US first class seats, and a lot cheaper. When I went to the UK from SFO last spring, it would have been roughly $1,000 regular economy and $1,400 economy plus. It was more than worth the extra $400. I did make my reservations 9 months in advance. Economy Plus seats are two-across instead of three, and you have a leg rest and a lot more space. If you get a window seat, you get a cabinet next to you that you can put your laptop and purse in or whatever.
And a really BIG secret. Did you know that you can bring water bottles that are frozen? As long as there is no liquid, you can take them through security. I have water bottles that can freeze and have started doing this.