It took an entire season of consistent minutes for Mason Mount to come out of his shell. Initially for Lampard he was simply an engine, which is why so many fans last season were riling up on him; they simply wanted more creative play and Mason Mount wouldn't achieve that for them. This season, especially in the last 2-3months, he's transformed into a much more creative player with great penetration through direct play, dribbling, and finishing. If he was getting 10 minute cameos and the occasional start every 2 months instead, he would have never reached his current level so quickly.
The comparisons between him and Puig are simply unfair to Puig.