You can't blame the writers for everything. Beltran and Montgomery got their episodes in which they could shine and Fortunate Son and horizon were great ... accept for Montgomery's performance. I don't wanna blame them, sometimes good actors don't match a role.
Beltran on the other hand never brought any interest to it. You could see how bored he was during playing and he later frankly admitted that he hated the show. Which is fine with me, it is after all just a job. But if you don't work hard you have no right to whine about not getting better scripts or more spotlight.