I feel we've been in the same spot as you. We had a wiki (google sites and google drive with a lot of documents) but information would become inaccessible from time to time, to the point it was pretty much useless. We eventually understood that the knowledge sharing/maintenance was simply being an extra step in our work, a mostly disregarded one, almost an after thought.

What we did was to put knowledge at the center stage, make it as easy as possible, pleasant to maintain, and avoid at all costs new/extra tools. We eventually settled for Notion. I'm sure you can find about notion benefits on your own, but essentially it does all that. It's super intuitive, easy and beautiful, easy to get around (albeit sometimes slow). Get everthing in the same place as much as possible, with every new tool you'll loose out (knowledge bits here and there, extra connections that stop working, or that people don't bother to check)

But getting a good information platform was only half of the story. We needed to start thinking and working differently. We decided that if we ever make a decision, or arrive at a conclusion, that's worth sharing, then it should be worth writing. And it's by doing this, and expecting all other team members to do it as well, that we arrive at this stage.

I'm sure this doesn't work for all teams, and other teams probably arrived at other, even better solutions, but this was what worked (wonders) for us.