Is the London system best opening for white?

There is no, "best opening". The london system is solid. You're building a pawn triangle and developing your pieces to good squares. It's a queen pawn opening, which means that games tend to be more closed and positional in nature.

It's easy to learn the opening at a beginner level because it's a system opening where you do the same 5 or 6 moves despite whatever your opponent does. The drawback of that is if your opponent is not passive and immediately challenges white, a newer player will have no idea how to respond since that would involve critical thinking... which the london system definitely does not strengthen at this level. So...

Pros
It's safe most of the time - you won't be challenged or encountering too many new positions
It gets you in the habit of activating your minor pieces (playing with your bishops and knights instead of leaving them unemployed on their starting squares)
King safety

Cons
It's safe most of the time - you won't be challenged or encountering too many new positions. (But challenging positions help you learn faster so you are potentially stunting your chess development)
After your initial setup, a newer player will have no idea how to proceed into the middlegame

Neutral
The game might be more positional in nature

Fair enough but I feel I'm quite good in the middle game but lack a solid consistent opening, especially on white. Thanks for the advice!

It is actually far more flexible and interesting than many say when you don't just play the system moves in zombie mode but start adapting to what your opponent is doing from move 2 on

Magnus Carlsen played the Bongcloud against So in an Online-Match. Wesley So said: "If I lose this I retire from chess." Well he lost it.

With this example in mind we can say you can almost play everything when you are a good player. The Bongcloud though is of course trash and should lose - normally. The London-System is instead a normal opening. But its not better or worse than any other normal opening.