I think some tech skills are important but overall tech skill is not what it's cracked up to be. It's also hard to define what is tech skill. To me effective movement is a large part of tech skill. You could have great spacing in your head but if ability to get the character where you want to go is bad then it doesn't matter.
On the other hand many tech skills can give your opponent a unique challenge but are not necessary. For example as fox, in a situation where a shine spike is possible, you could often also just nair off the edge, dair as they go for the ledge repeatedly and many less efficient options... it definitely helps to find new ways of doing things that are more effective BUT and this is my main point: I think a lot of online players suffer from using tech skills as a crutch and not improving other parts of their game. As Fireblaster said, at lower levels, someone with better tech skill can simply overpower another player without even outhinking them. Based on that you could just keep improving your tech skills to overpower even better players but there's a limit to this because there will be player who have a better balance of tech skills, spacing, and reading to beat you.
Overall I think that spacing allows you to capitalize on good reads and those two are only as useful as the tech skill you have to implement them. I think the best way to improve is to only use tech skills as a means to an end, keep you tech skill up to par with the rest of your gameplay but don't let it surpass it or improvement slows.
