From the beginning of FIFA 18, Left Back has been the position I have made the biggest research for the best possible player. Every list of players I find in the forums is either not even mentioning this guy's name or describe him as "not bad".
From my experience out of more than 400 games with him protecting my left side, he is a Top5 at least LB in the game this year.
And let me explain myself.
I have used Alex Sandro, who is actually really good and even used in squads full of icons.
I have used Alaba, who -for me- is a bit better than Sandro due to his better Weak Foot mainly.
I have used Jordi Alba who fits my playstyle perfectly.
And these are the best Left Backs for me this year in the game until now (3/1/18).
But in Premier League we have IF Marcos Alonso, IF Young, SIF Young, IF Zeegelaar, IF Baines, IF Kolasinac, TotGS Blind ...and Rose.
Everyone of them is lacking something and is perfect in some other aspects of the game.
Both of Young IF cards are fast and agile but not strong enough, Baines is slow, Kolasinac is a defensive beast but he feels like he cannot turn, and Blind is an excellent CDM but not a Full Back with that pace.
Marcos Alonso has the best stats in my opinion but he feels really slow in the first meters of his runs, and this is all you need if you play a "tiki taka" style - Acceleration.
For me, Danny Rose regular card is the best because he is a "jack of all trades" in this position, and he lacks nowhere too much like each one of the others.
He has decent pace (with a SHADOW card he feels fast) he has the best Defending attribute alongside Kolasinac (without being so "robotic" though) his Acceleration is the highest, only after Young (who is right footed and much weaker) and his Passing and Dribbling Attributes are "acceptable" for his position.
Plus he has the best Working Rates for a LB in my opinion.
Danny Rose normal card is good enough for much less than 5k, and all the others mentioned are at least at 20k-80k.
So, just save your coins and strengthen another area of your team.
Danny will cover for you for a minimum cost.
Passing (could be better, it is decent though)
Strength (some more strength would help him never being pushed away)
Stamina (this is the worst stat of his card, although it is 81, which generally is not very very bad, for a Left Back it is quite bad)