This quote suggests a progression of roles that people might assume over time, starting as witty individuals, then becoming poets, then critics, and finally being perceived as fools. The progression implies a shift from creation (being witty and writing poetry) to criticism (evaluating others’ work), and then to folly (perhaps through misunderstanding or misapplying their critical faculties).

The first part, "Some have at first for wits, then poets passed," suggests that people initially gain recognition for their cleverness or wit, and then use that recognition to establish themselves as poets. The transition from being witty to being a poet implies a move from casual or spontaneous cleverness to more formal, structured expression.

The next part, "Turned critics next," suggests that after gaining some success or recognition as poets, these individuals then turn their attention to criticizing the work of others. This could be seen as a natural progression, as success in a field often leads to a desire to define and enforce standards within that field.

The final part, "and proved plain fools at last" is a critique on those who have moved from creation to criticism. It suggests that in becoming critics, these individuals have lost something essential, perhaps their creativity, originality, or joy in the work, and have thus become "fools".

Applied to today’s world, this quote could be seen as a warning against the pitfalls of criticism, particularly in the age of social media where everyone can voice their opinions and judgments. It suggests that while it’s easy to critique others, there’s a risk of losing one’s own creativity and becoming a fool in the process.

In terms of personal development, this quote could be interpreted as a reminder to keep creating and innovating, rather than getting stuck in a cycle of criticism. It’s important to learn from others and to critically evaluate one’s own work, but not to the point where it stifles creativity or leads to a negative mindset. Instead, one should strive to maintain a balance between creativity and criticism, thereby avoiding the risk of becoming a "plain fool".