If you ask me SEO is over rated, I worked for a bespoke SEO/SEM company in the UK for about 3 years
I was responsible for blue chip clients, running their Google accounts, managing keywords on and off-page, as well as code cleaning, optimising copy and optimising keyword density & placement
If you have the money to pay someone on a day to day basis, then yes, it can help, but you need a site that will be updated on a regular basis and with that, it needs to grow
I've been running 2 of my sites since 2007, they are updated on a regular basis, are sites that can be trusted and so far as I can see Google sees them as authority sites. They have been in the top 10 since 2007 for all of the search terms I want them to be found for, that's 14 years
BUT, I don't do SEO on them 🙂 they are well coded, use semantic markup and that's it