"I want to be in top 10 of SERP, here is my competition, now I know exactly what to do to get to top 10".
unfortunately, I'm not an expert SEO, I've never ranked in tough niches so I'm not the best person to answer this question.
But since you asked... probably the best way to get there that works most of the time is to get backlinks. It's stereotypical response, I know, but that's because backlinks are still one of the most crucial (if not the most crucial) ranking signals, so if everything else fails I guess that you could get into top 10 with good, strong backlinks...
This also sounds like one could spend a lot of time generating a lot of content to try to boost SEO...but result in little impact.
in tough niches you can have all the content you want, you won't rank without strong backlinks. In easier niches, however, you might rank mostly with content and some basic SEO (internal linking, topical authority, technical SEO, etc)
It depends on your situation really, that's why I said in the previous message that we don't know anything about your niche + keywords, site and competition to be able to give a better reply, so I blurted out general info...
You are probably right that one needs to do it many times to get the hang of it, but man that sounds like it could also be a lot of wasted time.
do what many times?? If you're going to have 100s of sites, then yeah you're going to do "it" many times, but you can automate most of the things, so in the end you don't have to do it many times.
Anyway, SEO is a long journey, this part is true. You want to rank in top 10 for a tough and profitable keyword and after 6 months you get there? Guess what! The next day / week / month someone will outrank you or google will change the rules and you need to start over: analyze what happened, figure out how to fix it, fix it and rank again, sit on the edge again in fear that google will change the rules again (which they always do), and so on...
Now bare in mind that I'm talking about the little guys here, people like you and me (or maybe just me, maybe you're filthy rich and can manipulate google to your liking), for people with deep pockets this is easier: just throw $100k / month at the best backlinks you can get and rank within 1 week!
This does happen, but if your SEO budget is limited and you're a newcomer to this industry (new domain, no content, no backlinking history, no SEO knowledge) you're going to go through ups and downs, this much I can guarantee
Given how inexact of a science this is, are there good ways to evaluate who is good at SEO?
I'm sure there are ways, but I don't know them... Before hiring someone in the past, I used to ask for guarantees that I'd get results and some of the providers were able to give guarantees but most of them weren't. But guaranteeing results was a good way of knowing who's good at SEO, at least for me it was, I always felt comfortable being guaranteed results because if things failed I had grounds for holding the providers accountable and demanding my money back.
But guaranteeing results nowadays is very tricky with google's endless updates that can screw you over, so I understand why most SEOs don't want to do it anymore...
Another way would be to check the testimonials and reviews they have, but these can (and oftentimes are) bought so I almost never trust them. I know that Amazon is not SEO provider so the comparison is not fair, but the point stands: Amazon are buying and faking reviews, so why wouldn't SEOs do it? Besides, I've been asked in the past (12-13 years ago)) for fake testimonials myself, so I know that these can be faked / bought
And lastly, another way I can think of off the top of my head to figure out their skill is to simply buy a test service from them and see how it fares. Although, this has its drawbacks too, because some sellers provide you a top quality service initially to hook you in, and then they expertly manipulate you through paying them more over the long run while providing only minimal results. So, this is not a 100% safe method either, but it's one way of doing it...