IMO CGS got it right by going to 100 as the top grade. It's something TPGers in the USA failed at when they started up.
That's always been my general rule for interpreting UK grades: just take the US grade and bump it down 1 full grade. I have no idea what it's worth, but I like it, details slab or not. IMO, with really old coins, you have to almost disregard any "details" notations and just decide "do I like the look of this coin or not?" This is something I learned from collecting ancient coins. Almost 100% of ancient coins have some sort of problem, whether it's something as innocuous as being off center (which generally isn't even considered much of a problem), all the way down to serious and badly done tooling (which is considered a serious problem), or even bronze disease (which is not only considered a problem, but it will literally turn the coin to dust if you don't do something about it). With ancients, you have to pick and choose what problems you'll accept. Broadly appreciating ancient coins requires a real sense of wabi sabi. Newman started collecting in the 1930s, IIRC. I would wager the majority of his collection was assembled before the 1980s. Grading didn't start to go seriously off the rails until sometime around the early 80s, IIRC. OTOH, collectors were generally encouraged to clean their coins before about the 1960s. Any kind of toning was considered such a negative it was worth destroying an original surface to get rid of it. "Brilliant is best," after all, right?
The TPGs have provided some sort of standards, even though they may differ slightly. Prior to the TPG, some dealers took advantage of their customers and some just did not know how to grade. The same is true today only it is harder for them as the TPGs have rendered an informed unbiased opinion. Not that they always get it right, but it's better than relying on someone who is making a profit off of you. As for the 70 point scale - it really doesn't matter if it's 70 or a 100 as long as they stick to the grading standards - which they have not. Grade inflation. That is the biggest problem for the TPGs.
I'm obviously not anti-TPG, but what used to be the dealers screwing over people by inflating grades scribbled on 2x2s in their cases, is now a game of maxing out the grade on a coin entombed in plastic. While the TPGs may be offering (mostly) informed and unbiased opinions, they are still just opinions. In more recent years, the TPGs have started charging a percentage of a coins value for the slabbing - the "unbiased" component could be called into question as the TPG now benefits financially from grading coins higher. That "development" is a very disturbing one. No amount of external opinion replaces a person's own opinion, knowledge, and experience.
Your last statement says a lot. The problem with it, however - is that there is a significant lack of knowledge and experience in the hobby. You are correct that Those who are experienced and knowledgable - should trust their skills. To comment further by asking a question - how many dealers now have the knowledge and experience to grade a coin correctly? A large percentage have the skills, but many now seem satisfied to rely on TPGs. I'll add that there are too many grades, too many optimistic graders in the hobby at the movement and as you mentioned a financial motivation by the TPGs to inflate grades.
I agree on the comments. One reason I only buy from companies that take returns even on there slabbed coins unless the photos are perfect. In this day and age with covid I am buying everything online , half the time from subpar pictures. I have gotten a few great deals off auctions with bad pics but I still like the idea of being able to return the coin of it arrives and does not look as expected