While I agree, I think the fundamental issue is that the concept is broken, which is the problem. You could say that in certain circumstances you succeed if you hit a DC 15 like acrobat. You could get advantage on your next attack or ability check ala Sherlock Holmes but that's already taken by Empathic. You could think of some clever way to assist someone ... no that's Historian.
The structure of proficiency bonus + some unique cool power associated to that ability is the issue. There's just not that much room for unique powers that aren't overpowered or change the flavor of the game that also mean something when you have 18 of them.
I feel for the author of the article. I do. Because if this were a previous edition of the game it would be easier. You could have looked at the rules for stealth and given a specific advantage that was not already indicated by the specific rules instead of giving a specific (overpowered IMHO) rule in a system that was purposely left vague.
So my suggestion? Maybe just the proficiency bonus - and the proficiency bonus alone - is enough. They're already half feats, do they need anything more?
Well, the benefit works fine, as is. It's just not a particularly useful benefit, at least IME, because it's so narrow. The only time Search as a Bonus action is going to come up is combat with hidden creatures, and the occasional "gotta find the mcguffin and do the thing with it while the doom clock counts down" scenario. Pretty much every other feat is useful a lot more often than that.
But I'd have no issue with it if it were just part of a feat. Or a small class feature, etc.
Also, yes, the feats do need more than proficiency. Look at the half feats in he phb, other than the sad AF Linguist feat. We switched that to this still of feat, bc we have the Riddle skill, which covers cyphers, translating text, and speaking in and understanding coded language. Side note, I've mostly seen players take these feats to get proficiencies they didn't have, so far.
Some things Investigation handles are;
examining something to learn about it's past. "The door handle is well worn, as is the floor in front of the door, this room is accessed often." Or forensics stuff like examining a body for clues.
Research? Or am I adding that to my games because I do a lot of investigation?
What it doesn't naturally do, I would say, is allow for big jumps like Sherlock Holmes makes. Or to learn things normally covers by other skills, examine magical effects to deduce their purpose...all things a feat could add.