I feel that recent changes in the WP world are not yet reflected on Themeforest.
Elementor and VisualComposer create slow-loading sites, while Gutenberg has become stronger. Yet, there is no way to filter for Gutenberg themes.
Nearly 90% of the themes coming up in a search are Elementor or VisualComposer and I have found no way to search for Gutenberg inside those search results. However, I can search fur Gutenberg and do get sensible results.
Please consider to adjust the filters.