Whitelisting is a decision that would mostly either maintain or decrease a current player base for SA-MP's (and therefore Ls-rcr's) situation. Whitelisting, if it works as intended, will decrease the number of "low effort players" (regardless if they're cheaters or not) and will increase the number of "high effort players" (regardless if they're cheaters or not).
Situation with SA-MP, GTA SA, and modding in general is very volatile. Regardless of remasters or not, it's unlikely that T2 and Rockstar will ever be as open to modding as they were with SA-MP and MTA (can primarily thank Hot Coffee and piracy for this). Therefore, it's not dumb to assume that SA-MP has a stagnant or decreasing player base, with occasional visits from nostalgic fans or younger players that want to see what the old games were about.
On top of that, there's no reason not to look at the other SA-MP servers around. Many of the RP servers in English have closed down due to diminishing returns or interest in moving elsewhere (GTA V or otherwise). These servers were often at the forefront of arguments such as "SA-MP is not dead, but rather Ls-rcr is dying", and now many of them are gone. If things had such an overwhelming positive outlook, it'd have been harder for people with that much experience to all have made a mistake at the same time.
The paragraphs above all lead to the following conclusion: you cannot steer the natural course of things. Many "high effort players" (those that have a bit of a stronger English, will form/fund groups, follow the rules, potentially be Staff, etc) are really mostly interested in a community where there is enough stimulation from the rest of the player base in a similar way to what they are expecting. This doesn't necessarily hold for "low effort players" - because of the situation above, they are in abundance in comparison, and as such find many other similar people to relate for and therefore can enjoy their experience in the game. In short, there's a generational & socioeconomic crash between the "old" players and the "new" players.
Whitelisting, imo, would then at best turn Ls-rcr into a friend group server of at most 30 people with very little or no new players coming in. If the server would adjust economically and all to this change, there's no reason it couldn't last as long as the last person's interest in the game fades. Remaining on the same course of action may lead to the high effort players completely leaving the server, at which point the low effort players would suffer a similar "suffocation" result.
It's tough to say, and many other servers have faced the same dilemma and came up with their answers. In short, I think it is mostly up to server management to decide how to market Ls-rcr from this point forward, taking into consideration what has, is, and will happen to SA-MP. In simple terms, I'd be neutral to this suggestion for that. Nonetheless, I'm forever grateful to Ls-rcr for being the place where great memories were formed, with both low & high effort players.