It's like if you never PvP just don't press the button.
Also it's not P2W or a road to P2W, it gives cosmetic rewards.. for money. For you it's better if Blizzard gets richer from other people's money who you don't know as they'll have more resource to make the game better.
A bit other topic, but even if they make Boost to 90 a payable thing.. why care so much? Maybe the guy will be too noob to play the class properly at insta90, but if yes he won't even reach your level of gameplay content so you won't meet him or get drawn back by him. What if the guy is your guildmate who is playing for 8 years and your guild needs a good healer so bad instantly, or your arena mate rerolls to reach ratings with a class he already maxed 5 times before on other realms?