Some weeks ago I've been to France and stayed at a hotel near one of the suburbs next to Paris. Walking around there, what amazed me was that there no children anywhere in sight, with the only exception being a (hilariously meme like) white grandma taking her two black grandsons for a walk (guess the daugher had very poor life choices).
Yeah, in first-world countries we thankfully don't have gaggles of 6+ kids who we can't support like they do in ghettos or 3rd-world countries. Part of the reason people had "more children" in more primitive times (in additional to possibly lacking birth control) was due to higher expectations of infant mortality, or wanting a larger family to aid with menial labor such as farming which was more often necessary in less developed circumstances.
This has probably been the case since the days of ancient Rome and beyond (people in more developed circumstances don't need to have as many children as hardscrabble, survivalist 3rd world countries due, since death from childbirth and infant mortality is less common).
A "nation" doesn't even need everyone to have children or have "more children" to sustain itself. A "population statistic" means nothing. unless you just want more human cannon fodder to send to war (and even then, a "large population" fighting with swords and spears would lose to a modern military or "less population" using fighter jets, tanks, aircraft carriers, and ballistic missiles).
Ideally, it would only be the responsible members of society having children to begin with, and as far as the nation as a whole is concerned, a lot of the stuff which currently is doesn't need "replenishment" and would be better off disappearing at no expense to the nation (e.x. if the ghetto families who do nothing but have gaggles of children they can't support and were left to the expense of the state to raise simply stopped having children and disappeared, society as a whole would be better off, other than maybe the politicians who want to use them as a source of free votes).
This forum talked a billion time about white replacement and mass immigration to make Europe non-white,
"White replacement" is a stupid conspiracy theory that only stupid or illiterate people believe in. The vast majority of immigration (including illegal immigration) doesn't have anything to do with that, it's just people following their own self-interest (or financial interest, such as in the cases of companies illegally hiring illegal aliens off the books to save money). If all you can do is point out some random nutcase like Brittney Cooper or the New Black Panther Party who "hate white people and wish they were dead", that's not even a blip on the radar.
Unless they start banning white people from reproducing, or forcing whites to procreate with non-whites you have no claim to make (and even if that was happening, it wouldn't be any different than Nazi eugenics - just with the skin colors reversed, so there's no way a Neo-Nazi can claim some type of moral highroad on the matter). Just because some incels and virgins can't get laid consensually due to their bad genetics isn't the result of a "conspiracy to stop whites from procreating" no matter how much these fuckers want to believe it.
Basically you just hate that evolution isn't favoring "whites" (most of whom aren't even very genetically "pure" to begin with and have never been DNA-tested but just happen to "look white") over non-whites in the natural selective department. Evolution doesn't give a fuck about someone's quaint little invented notion or "whiteness" anymore than it does about the thousands of other races or people which "diet off" because their genetics weren't fit enough to survive.
but the truth of the matter is that Europeans seem to be completely averse to the notion of a next generation to continue their lineage/take care of them when they're old.
So give your best ideas how to fix it.
What the fuck does this even mean? If you're talking about publicly-funded social program or social security which every taxpayer pays into, this has nothing to do with the level of melalin in a person's skin.
Simple, ban birth control methods.
Better idea, just go move to Sub-Saharan Africa or another 3rd world nation lacking in any modern contributions to arts, sciences, culture, mathematics, and so forth. Since the "culture" you're looking for would basically be 100% identical to that of Sub-Saharan Africa, just with lighter skin. You'd fit better in with the culture of the n*ggers that than you would with "white" people in any actual 1st world country.
Not to mention that birth or population control has existed in every culture from ancient to modern (e.x. ancient laws with harsh punishments for adultery or fornication existed in part to ensure procreate responsibility and prevent children from being born without means to support them, and even exists in the animal kingdom as well):
Ants That Illegally Procreate Are Revealed By Their Guilty Smell
www.discovermagazine.com