Guys I couldn't give merit for I am also one of those who struggle earning it, what I can give is a sort of moral support, for I know many here lose hope of ranking up because they failed to get merit after doing their best in constructing "quality post".
Just imagine this guys, when we rank up and become a "member" at least, opportunity to earn from signature campaigns can surely help us on our finances, try reading and continue learning, the higher rank we get in, the more chances of earnings.
Continue working hard and don't give up, rewards are coming for those who never stop trying.
I think your mindset is wrong in this case. You can participate in other types of campaigns, such as social media and creative media. The signature campaign is just not worth the reputation compared to payout (and risk) for a peasant like us.
And also without a linked account, it's impossible to rank up without doing something meaningful to the community. Just learn and create your best quality thread once a while when you have spare time. Just relax

You are partly correct with the fact that one can join social bounty campaigns if he's not eligible for signature campaigns yet but remember that only posting on bounty threads would not lead in increase of your post quality in any way and you might lose any potential merit points that you would have got if you posted constructively.
You must balance both of them, because signature campaigns provide opportunities to earn in bitcoins eliminating the risk of getting payed in new tokens.