5 sec is way too long. Don't hear too much issues regarding reverse, but man these 10R80 will come back and bite Ford later down the road when more of them fail. It will expose their defects and short comings.
In the end. Get what you need, want, or budget for. Everyone has different priorities. My tuned 2019 Lariat fit my needs and put a smile on the my face. The RR just puts a bigger one. I had all the intent to keep that 2019 for a long time but speaking for myself I'm glad I upgraded.