I wouldn't put it as ripping people off - there is actual science behind their formulation and all otherwise Shell would've been sued by someone ages ago kinda like how Castrol was sued for their Magnatec range.
There are reasons why older cars vs newer cars can't really go with the same oils. Even Penrite has their "classic car" range of oils that are more suited for classic cars vs their newer HPR / Enviro range of oils. I cannot recall the reason but you probably can research it yourself (
www.penriteoil.com.au/products/brands/classic)
If you do a quick google :
What Are the Risks of Switching to Synthetic Oil in Older Cars?
There are reasons la.. it's not to say bullocks altogether.
Actually there's nothing wrong with group 3/4 oils. Most brands run group 3 or 4 except their racing or top end ranges that use Ester base oils. Then there's also the different qualities of group 3/4 oils. Have a read here :
All oils are made up of base oils and additives. Not all base oils are created equally however. The API classifies these into 5 main groups. Group III and IV base oils are 100% synthetic. Some very high quality Group II oils (called Group II Plus) are also accepted as having synthetic like...
www.penriteoil.com.au
Don't get caught up too much in group 3 / 4 / 5 base oils. Most modern reputable oils these days are more than well blended with the good stuff. The only things we need to focus on is the additives and how it works / reacts with our cars.
I mean you should know - you use a diesel oil in your car. Kaokao detergents in your oils