Where the missing multiplayer might surprise you in a bad way, the new level scaling system might be perfect for you.
Level Scaling Explained
As you boot up Mass Effect Legendary Edition for the first time, you might be surprised by this option at the start. Under your gameplay tab, where you can change around your difficulty, levelling structure and a few more things, you have the level scaling option.
You can flick it between class and legendary mode, suggesting which one is the new one. It says "In classic mode, the original 1-60 level range will be used instead of the new 1-30 level range. XP and talent points progression remains the same, but the number of levels is doubled"
As it says in the description, legendary mode gives you a level cap of 30 rather than the standard 60 but the base difficulty of the game is the same. This gives a slightly different levelling experience.
What Does It Mean?
You will level up half as often but those levels will be more powerful. It's a way of removing the more incremental level builds of Mass Effect, allowing for more substantive differences.
If you want to influence every moment of your game to achieve a certain build, you will likely prefer classic mode. This will allow you to level up a little more and allow you to build out your class slowly. If stat building is something you care about, this is your mode.
Legendary mode is much more simple, allowing you to stress your build a little less. If you have an idea of what you want but don't really care how you get there, this is the mode for you. If you just want to get out of the menus to start fighting bad guys and punching annoying guys, get started in legendary mode