this is some weird analysis. Even Jamie Bloody Carragher is talking about how United looked like a team that was playing with only ten men because the one player tasked with linking the midfield with the front two (Mkhiyatran or whatever his name is) was so poor it looked like United were playing with ten men. Swap Mkhiytran for Harzard and vice versa and your "modern" striker (Morata) would be dreadful too (funny enough Lukaku does just fine playing with Harzard for the Belgian national team). But back to your modern forward theory, Lewndoski and Costa are the best target men in the world, yet they are playing really well, today, for top clubs. Why? Simples, they get good service.
Lewandowski has more to his all around game than Lukaku. It's like a different level.