Depends, it has certain training missions, a low level gamemode so new players play together instead of them getting destroyed by level 200+ players.
Not pay2win at all, but i'd love to see you explain as to why you think that way about it.
Maps too complicated? In what way? Layout? You can walk through it and/or learn the basics from t-hunt, casual or god forbid, the internet.
There are some bad maps though, but every game has those (lets not talk about Canals, different versions of nuke etc.)
Guns and customization? For most rifles, there are 3-4 scope options (three 1x sights and in some cases a 4x scope), two options regarding grips, 3-5 barrel options and a laser. How is that complicated? You get a description of what each attachment does and how it'll affect recoil, sound, or ads time.
Haven't watched enough rainbow six esports to comment on the last bit.