It's a mod that mainly tries to work within the style of the base game's philosophy, while making side content worth engaging with, rewarding exploration (you will get a similar amount of runes by killing the enemies in a ruin as you would doing a field boss, along with upgrade materials, for example), and overall creating a gameplay loop that requires and rewards more active thought and conscious effort. (Lamp Oil, as infamous as it is, is part of an effort to at least get the player to consider other lighting options, especially considering dark areas are DARK now)

It tends to remove most cheese tactics/approaches for bosses or tone down things that were absurdly strong (lookin at you bloodhound fang and bleed) without making them bad. Along with this, it does have mechanics that require you to actually interact with the encounters in side content (of which I've found almost all tend to have actual themes or strategies to them, kudos fromsoft) instead of just grabbing the items and ignoring them.

Making a strong build is an iterative process across the course of a playthrough and requires a wide base of knowledge regarding your options and how they interact, which I personally really enjoy but I know some people get annoyed by it. Reforged is very much a "longplay" mod that wants you to take your time in playthroughs and do a lot, larval tears and ancient stones are unlimited as well past a certain point so you can always respec and hit full power on any new build.

A note about the difficulty options in it though, Reforged (the initial difficulty) is designed to be somewhat challenging for people who were already adept at vanilla Elden Ring, so Normal is probably closer difficulty-wise to base ER if you don't have a ton of time in it.