This is the 4090th most frequent Japanese word.
ベタ
"ベタ" means "cliched," "predictable," or "basic" in a conventional and often overused way.
The word 'ベタ' is used here to indicate something predictable or commonplace in its nature, specifically referring to the plot of the movie.
その映画のプロットはとてもベタだ。
The plot of that movie is very conventional.
In this case, 'ベタ' describes the joke as being overly typical or stereotypical.
彼のジョークはベタすぎて、みんなが苦笑いした。
His joke was too clichéd, making everyone chuckle awkwardly.
'ベタ' is describing the directing style as being typical or conventional, common in older works.