As with any service, not just SEO, hiring a professional can drastically reduce the speed of the process. The work time is the same, and in the case of SEO, the speed at which results are achieved can be greatly reduced compared to doing it on your own.
The reason for this is that SEO companies and freelancers specialize in SEO and support SEO for various sizes and types of businesses, so they have by far the most accumulated know-how. Of course, they have not only successful cases, but also many unsuccessful cases. Failed cases can be improved, and successful cases can be horizontally deployed on various websites to check the results, thus reducing the probability of SEO failure.
On the other hand, there are of course advantages to doing SEO on your own, such as no new budget, the ability to accumulate know-how in-house, and no need to manage SEO agencies or freelancers. Although the opposite of these advantages, it still takes time to accumulate know-how because various PDCA cycles must be performed before success is achieved. In addition, SEO often takes a long time to produce tangible results, and it is often difficult to gain recognition within the company. Although there is no external budget, someone in the company will of course spend time working on SEO, and if the results do not produce the desired results, the budget for continued SEO will decrease.
It is necessary to consider the advantages and disadvantages of hiring a professional SEO agency or firm.