Generally, our current understanding suggests that planet formation is a complex process that occurs over millions to billions of years. It involves the gradual accumulation of dust and gas in protoplanetary disks around young stars, followed by the formation of planetesimals, protoplanets, and eventually fully-formed planets.
However, scientific understanding is constantly evolving as new data is collected and analyzed, and new theories emerge to explain observed phenomena. These new theories can challenge or refine existing models, potentially altering our understanding of planetary formation timescales or other aspects of the process.
To accurately assess how a new theory challenges our understanding, it would be necessary to have specific details or references to that theory.