I apologize, but I don't have enough information to answer why things might be slow for you lately. The knowledge sources provided don't contain any specific information about recent performance issues or slowdowns with Mixpanel.
To properly address your concern, it would be helpful to have more details about what specific parts of Mixpanel you're finding slow, when this started occurring, and any other relevant context. Without more specifics, I can't pinpoint the cause or provide an accurate explanation.
If you're experiencing persistent performance issues with Mixpanel, I'd recommend reaching out directly to Mixpanel's support team. They would be best equipped to investigate and resolve any technical problems you may be encountering with their platform.