LRV is still vastly underutilized during gameday. I know this, because I am currently designing the new CID station and we are looking at event overflow (line 2 CID will be about 1/3 mile from Lumen), but its not as much as you'd think in terms of passenger amounts (I have the passenger count on my computer). Its sad that LRV isnt used more for events, but it just isnt yet. So while Lumen has Stadium and line 1 CID, SF has Museum and 18th, which are nearly identical in distances to what Lumen has (maybe a tad more, but were not talking MILES here, maybe 100 yards more)
Also, train stations can be added to existing lines, or completely remodeled and upgraded to handle the event numbers. Thats literally what I do for a living
ETA: King Street station is near Lumen as well, but thats Amtrak and nobody takes Amtrak to a sporting event