Unfortunately, we are subject to getting junk mail either from the USPS or through our internet accounts. This a simple reality that complaining about will accomplish nothing. This is a fact of life and short of living off the grid with no internet, no US Mail, no credit cards, no public utilities, no bank account, etc. will change that. Just one of those pesky things like death and taxes.
The best suggestion to avoid spam is to never provide your email or US mail address to online sites or surveys. This is not a guarantee, but it might help.