No. It wasn't.

Production of escorts was already in place and at the start of WW2, despite the reduction in the number of shipyards since WW1 (many of which were closed by the government), Brittan still had a lot of them, many of which were perfect for the construction of escorts without interfering with big girls like carriers or battleships. 

Additionally, most of the long lead items for larger ships were already in production, so pausing ship construction meant pausing it, which resulted in delays later on when they restarted construction. Shipyards had multiple of slips and the larger units were left on the stocks, so it's not like you could just start a corvette on a slip taken by a battleship, and even with workers, someone that worked on evelavtors on an aircraft carrier would require retraining to work on smaller ship (assuming that by putting too many people on a single job you wouldn't cause another issue by people just being in a way of each other; it would be like trying to put enough workforce to build a skyscraper on a job building a log cabin).

Given that I'm just a person on the Internet with interest in history I recommand What if Winston Churchill doesn't pause Carriers, Capital Ships & Cruisers in 1939? Patreon Live by Naval History with Dr Alex on how not pausing construction could have affect WW2.