of course players can keep improving, even mechanically. Mechanics are likely to be the area of skill with the lowest amount of improvement possible. But players can get massively better in terms of game sense, util usage, discipline, mental aspects, tactial understanding both on macro and micro level and many other things. Derke today is far better than he was in 2021. Alfajer is much better than he was in 2022. Keiko is far better this year than last year.
BBL pcific can improve both individually as well as a team by being exposed to T1 environment for prolonged periods of time. Also they would likely recieve a better suporting staff that aids their development at t1 level.