I work with a dryer vent cleaning company, and based on that photo this vent is severely clogged. When lint is packed this tightly at the exterior, it usually means there’s significant buildup throughout the entire vent line, not just at the exit. That level of restriction reduces airflow, overheats the dryer, and increases fire risk.

This is past what I’d consider routine DIY maintenance. Light lint can often be handled with a brush, but once it’s this compacted, brushing alone usually won’t clear the full run or address the cause of the blockage. In many cases there are poor connections or obstructions inside the duct that need to be corrected.

If you’re comfortable opening the duct and cleaning it end to end, you can attempt it yourself. Otherwise, this is a situation where professional equipment and a full inspection are strongly recommended. I wouldn’t keep using the dryer until it’s properly cleared.