Bungie deservedly gets a lot of flak for putting things behind a paywall but not a single Destiny 2 will be mad about them doing it with Trials of Osiris.
Trials of Osiris is meant to be the pinnacle of Destiny 2 competitive play and the game mode features some extremely powerful weapons as rewards. Having prestige and the loot makes it an incredibly attractive activity but you have to be really good at PvP in order to be able to grab all the cool stuff.
Those who don't possess the necessary skill are either discouraged from playing the mode entirely or resort to cheating their way to the Lighthouse. It is this latter group that will stand to lose a lot more than what they paid for their cheats or recovery now since Trials of Osiris is no longer available to play for free.
As of Season 15, the game mode is locked behind the latest expansion, meaning you have to buy Beyond Light in order to play it. When Witch Queen comes about, that will be the requirement to enter Trials.
Normally, this change would sound like a greedy and unnecessary choice but given the rampant cheating in Trials that basically had no consequences due to accounts being free to create, it is the only logical solution. With cheaters' money on the line, they might stop and think twice before employing illegal measures.
With the introduction of BattlEye, the detection should also be better and alongside the payment required for Trials, it should make the activity much more enjoyable all around.