Not only are Belgian Catholics very accepting of SSM, the majority of U.S. Catholics agree as well (see link)
Your link is actually flawed...since "Intent" is vital to making a moral decision and the Catholic Church allows for intercourse WITHOUT INTENT to procreate, it's ban on contraception makes no sense...btw, if a poll were taken of this board, I'd guess that the percentage of members who use some form of contraception would be very close to 100%.
Unfortunately, the RCC has twisted itself on this issue...back when Vatican II was taking place there was a commission formed to address Family Planning (Contraception) and in spite of it being overwhelmingly accepted by that commission (see link below...go to the "Birth Control" section) Pope Paul VI and Cardinal Ottaviani (head of the Curia) ignored the recommendation, thus creating the problem we have today...i.e. not allowing the most effective means of avoiding Unwanted Pregnancies...the singular reason for Abortions.
https://www.catholicsforchoice.org/issues/
The fact is that the Catholic Church does not require every sex act to have procreation as a goal...and it is also OK to engage in those acts for pleasure only and definitely not intending to have children...therefore, the use of artificial means to achieve both ends (marital joy and family planning) makes perfect sense...so said the Vatican II commission.
Now, as to the relationship of this issue to Same Sex Marriage....a union of two people can be an expression of LOVE ONLY between them...btw, the Catholic Church blesses marriages between couples who are well beyond any possibility of procreation...i.e. LOVE IS LOVE.
Link: https://www.pewresearch.org/fact-tank/2020/11/02/how-catholics-around-the-world-see-same-sex-marriage-homosexuality/