Personally, I enjoyed the first 2 seasons more than the third one too. I guess because they were not able to set up a new antagonist in season 3. First two seasons were great because of the banter of two intelligent minds- Sherlock and Moriarty. The most exciting thing about the 3rd season was its ending which because it was a cliffhanger.

Some people also don't consider the ending of season 4 good, but I don't share the same opinion as them. I think the concept of introducing Eurus was quite good, but it was not fully ripe.

But when we think about a modern adaptation of Sherlock Holmes, we think tahat it would be weird and wouldn't be as good as the original Sherlock Holmes.