There's no doubt Diablo Immortal's Legendary Gems system

The issue is apparent. If you spend money to buy dozens and dozens of Legendary Crests will not only have greater Legendary Gems than people who only purchase D2R Items, for instance the battle pass but will also possess more of the game's most highly-powered 5-Star gems. 

Simply put, free players, will never be equally powerful as those willing to invest thousands of dollars. While there are technically options for players that are free to play to get 5 Star Legendary Gems for free, without spending money in terms that of making them, this is so long-lasting, resource-intensive and based on luck that you may be better off not even trying. 

Players who invest money will be more successful than players who do not by an enormous margin. It could be a good thing this only applied to PvE areas of Diablo Immortal such as dungeons, raids as well as Challenge Rift leaderboards. However, it applies to PvP too which is the main element on Diablo Immortal with its new Cycle of Strife system that puts two factions of players against one another , as well as the addition of PvP battlegrounds. 

While the game's combat Rating stat is limited during PvP matches to ensure a more level playing field, the amazing Legendary Gem effects buy D2R ladder items, as well as the Resonance boosts for stats the gems offer aren't and players clad with the most powerful legendary gems with five stars (which, once again, are only available by spending money) are guaranteed to decimate free-to-play players.