It’s definitely both a personal and a financial decision.
TR has gotten very good in terms of prescribing workouts. Sometimes blending the outdoor rides, especially when unstructured, can be tricky, but otherwise it does very well. Even if you go the route of wanting to prescribe yourself the efforts, the huge workout library with progression level scoring makes this very easy and effective. AI FTP has been a game changer.
To me the benefits of a coach are beyond just prescribing the workouts. It is having someone to talk to and help you work through challenges on and off the bike that could be impacting your training. In addition, I talk to my coach about gear choices as they have (or are) competing in similar, and at times the same, events and have a lot of info depth knowledge of the courses and my abilities. I also plan my race schedule with my coach. For newer racers, a coach that can help with “race-craft” and strategy is hugely helpful. Some coaches will also help you to incorporate other workouts off the bike, such as strength training. This is an area that TR is weak in. A month of coaching commonly costs more than an entire year of TR, so this is where the financial aspects must also be considered.