So who makes the decision on what is accurate Vs inaccurate? Who does the banning?
The main goal is to take the human bias out of the loop. You can still throw a wide net, with your tags. That might even make sense, with a more niche topic. At the same time, a set of tags that closely match your search should be rated higher than one that just happens to include it. A split weighting system provides a soft pressure towards better behaviour, without being authoritarian about it.
Tag spam would make this feature far more useless and an ordering bias.
And how would that work between instances? One advantage of tags is that it would make searching between instances a lot easier. Unfortunately, you would end up with a race to the bottom, with the allowed number of tags. It would quickly become useless due to spam from instances with less interested admins. It also lumps a lot more work onto the mods and admins, for no good reason.
Basically, your idea actively fights the nash equilibrium, something I’ve never seen work well, longer term. It’s better to change the underlying pattern and so change the equilibrium. This makes the system a lot more self correcting, even when people try and game it (and it will be gamed).