Polyester is the most common fabric in cycling jerseys for good reason — it does an excellent job of wicking sweat away from your skin and dries quickly, which is exactly what you want when you're working hard on the bike. It's also durable and typically more affordable than other options, making it a solid choice for most road, gravel, and commuting riders.
The main downside is that polyester tends to hold onto odor more than natural fibers like merino wool. If you're riding multiple days between washes or are particularly sensitive to smell, that's worth considering. But for most riders doing regular rides with laundry in between, it's rarely an issue.
One tip: check that the jersey includes a small percentage of elastane (usually 5–10%) blended with the polyester. This gives the jersey stretch so it fits close without restricting your movement, and helps it keep its shape ride after ride.