First they need to clean up the UI and make it better, make the game more friendly to new players, and implement those holding hand guides that almost every browser game have, i mentioned this in some other thread, like "1- create a player, 2- spend skill points, 3- enter a team, 4- play a game" and give in the end bonuses like 1k flex points.
Then they need to ressurect the game, spend some money in marketing, send emails to old players, facebook ads, etc, saying that they are trying to renew the game and stuff, a lot of games does this (heroes of the storm, evolve, for honor...), with a "new" name, like glb2 phase 2, glb2 enhanced or something, change the main page, colors, the logo, make the game look new, have a juicy flex point sale for new players and returning players, AND STOP CALLING THIS AN MMORPG, use football simmulation game.
Make people want to buy flex points and play for long, go a bit sellout, give 1 more S* for accounts that buy flex, or just straight out sell one S* slot for flex points, like 1k.
Also the marketing needs to be immediatly before a new NFL season, of before the playoffs/superbowl.