No you do not need a HUD to be successful, but it is not going to hurt you to have it. Even if you don't want to use it for player stats, the ability to analyze your game from a statistical perspective and easily replay hands is invaluable.

Thanks @phrikshin. This gives me alot of clarity

on some pokersites you can't use hud (anonymous tables...) so it depends where you wanna play. However having basic hud will help a lot in countless situations

I agree with the other comments that a tracker would be very useful to improve your game.
I personly don´t use a HUD so of course i would say that it´s not necessary, especially if you take notes and be focused on the tables.

hi, seeris
Welcome to the forum!

At the beggining, a HUD can be very useful in order to gathering your stats and then you can make some sort of analysis. There is ton of free contents in the internet that explain how to properly use some HUD's stats.

Some players make some confusing interpretations, so you must be careful and understand how the statistics work behind the numbers. For example, I've seen some players make some actions based on a generic 3bet stat but they had only a few hands from villain, which is the same as nothing.

An HUD is helping you a lot for sure mainly, understanding who villains' frequencies affect your strategy when you choose an exploitative line.
i.e. , villain stabs a lot? Ok I can now increase my x/r or raise % in general.
It you don't use an HUD you can play with these percentages, also be aware that your brain isn't able to grasp frequencies correctly. For instance, a player could be very passive but in the last 3 hands he 3 bet 3 times, your brain would assume he is aggressive and make an incorrect adjustment.

Stats don't lie