At least some of the online games, especially the competitive FPS, could benefit from a system similar to Quake III, where the map creator basically had to define enemy visibility per-sector. That's more manual labor, yes, but modern software is too afraid of it for its detriment, often missing out on O(1) time complexity and simple, reliable solutions.

Maintenance be damned, because they keep abandoning projects despite all the overhead, abstractions and tech that should supposedly allow them to ship more - the management will de-optimize anything good through their short-sighted attempts to maximize throughput and profits regardless.