This is kind of semantics, but Jimmy Arias is actually the model of the modern forehand stroke actually, and Andre Agassi is arguably the genesis of the modern pro game style that evolved in the early 1990's. In the meta sense, Nick Bollettieri was the "father of modern tennis" and has a MUCH more obvious influence then Borg in 2019.
Borg's development and career preceded the modern racket era that was starting in the early 1980's, and it's kind of limited his technical relevance to modern high level play. The same thing is generally applicable to tennis in general, the introduction of larger racquets and graphite composites was such a profound change that the norms and techniques that preceded were made obsolete rapidly. (Polyester strings have had a disruptive, but less dramatic effect along the same line over the last 20 years). It's this consideration plus the change in media (and the distance in time since they played) that have made Borg, Laver, Rosewall, Kramer, Stan Smith, Tony Roache, etc..... marginalized to a degree.
Nick Bollettieri is a slick salesman. He lucked in with Seles and Agassi and then Sharapova. They have all made their mark in the sport. But if he was so great, he would have produced a lot more elite players than he did. Tens of thousands of players have passed through his Academy over the decades. But he has only produced four or five notable players. And I would argue that they would have all been successful regardless.
Your points regarding equipment are interesting ... but hardly pertinent.
Equipment doesn't make Great Tennis Players. Tennis Players make Great Tennis Players. The things that stand out about the Great Male players of the last 60 years, Kramer, Rosewall, Laver, Borg, Lendl, Becker, Sampras, and the current Big 3 are their MENTAL prowess.
People say it is difficult to compare players from different eras because playing conditions, competition and equipment was different. I don't buy that. Every player is a Human Being. They all have Human Brains and are subject to Human Emotions. It is the Brains and the Emotions, the Human Mind and the Human Heart that can be used to compare players from ALL eras.
At their peaks, Laver and Borg had Mental Prowess that is unparalleled to this day. Djokovic probably comes close to those two. The rest are a long way behind. You would think in the modern world of Sports Science and Sports Psychology, modern tennis players would be mental giants. But for the most part, they are mental midgets.
Who would you want to play for you to defend the future of the Planet? Laver? Borg? Sampras? Federer? Nadal? Djokovic? The answer is easy for me. Either Laver or Borg by a country mile.