I think there might be confusion with the words being used. We here words like Casual, Hardcore, but these word definitions can vary and be much more complicated. So I will explain a few of my interpretations.
Casual – This type of player enjoys the game at a slower pace due to either time restrictions or just because they choose not to invest heavily in the game each day.
Hardcore – This type of player invests lots of time and effort into the game.
Competitive – This players approaches the game with a professional attitude, hoping to compete at high levels. They often study a game’s forumlas and any bit of data which can help them gain an edge over other players.
Non-Competitive – This type of player just plays a game for fun and has no interest in competiting at high levels. They may however still enjoy a bit of professionalism but not at the expense of any enjoyment.
Now when it comes to the LP system, it is simply a system designed for Casual Non-Competitive players. These types of players are into playing the game but may not have much time to invest in it every day due to RL and may also find long slow grinds boring. The LP system helps these players to progress the game at the pace that is better suited for them.
Casual Competitive players will find that unlocking full destiny nodes without any grind to be detrimental so Casual Competitive player will grind atleast the first 20% before using their LP.
Hardcore Non-Competitive Players will likely spend most of their time grinding everything and will utilize the LP to unlock portions that are either dull to them or just to speed up the progression a little.
Hardcore Competitive players are the ones that will not only grind out the most that they can but then will specialize in specific trees and utilize LP to jump past their competition assuming that their competition is not using their own LP in that same tree.
Now with this all in mind, the LP system as I’ve said before is not supposed to help Casuals catch up or even be on equal levels with Hardcore Players. The system mainly benefits the Casual Non-Competitive players who might get bored of the long grinds and just quit the game too early because they feel like it will take them forever to get just the basics unlocked. This system does not threaten competitive players and as mentioned by Dagother, eliminating the alt characters wouldn’t even solve the problem assuming there is one. Players can freely make multiple accounts as long as they do engage in certain activities with those multiple accounts. (No need for me to list all the rules on that.)
Now because LP is time gated, there is no way for someone to utilize LP to jump ahead of another player who is doing the same exact thing. Technically even if they were doing different things: example One player is maxing out wood chopping and pools all his LP into that, the other player is maxing out Ore gathering, neither player would be unfairly ahead of the other because while Player 1 is ahead in wood he lacks in ore, and vice versa.