I tried training - playing 6Max on the Advancedpokertraining website. Not as a full member(which gives you the complete analysis) - but as a free member.
You get to play against bots which for the most part play just like in Nathan's videos - calling with anything ( on easy difficulty which is the only free one you get on the site)
I followed Blackrain79's strategy to the book and tried to go 1000 hands just to see where I stand. That means no playing marginal hands whatsoever, TAG style to my best understanding of it, playing in position, value betting my premium hands, 3-betting to defend the blinds with the better hands, following the charts etc.
I managed to reach 1000 hands only one time without losing my whole stack ( I acually got 2x profit or something like that)
Ever since, I cannot make it past 400-500 hands without getting stacked- the coolers keep on coming.
IRL I have 3x profit at the moment(15 euros investment which I managed to turn into 60 recently)
With the plethora of training websites, videos,
Apps etc nowadays, it is a lot more difficult to be a winning player these days. A lot more people know a little bit more about poker gameplay in general - I think the mindset is the major factor which makes a difference, as well as finding the very worst of the worst opponents, like villains who will call with deuce 4 on a Q Q J 10 board. And there aren't half as many as back in the day when he wrote the books.
Otherwise it's "take my money today, give me yours tomorrow" situation for most of the time. Might as well play the lottery than making a profit at the micros these days.
I am not bashing nor questioning Nathan's advice regarding poker at the micros, on the contrary, I am extremely grateful to him for what I have learned from all his videos and books.