There are different attitudes to be found in Devarim itself in regard towards the Canaanites. On the one hand in Chapter 7 it says that the Israelites must destroy the Seven Canaanite nations completely and not intermarry with them. Well, if you destroy them then of course you cannot intermarry. But then in Chapter8 Moshe says that God will not let them be driven out right away. It will take time. Because otherwise, if you depopulate the countryside, it will go to waste. One had to be realistic. Nevertheless, the goal should remain, even if it was and is impractical.
From this it is possible to learn that the Torah did not expect a complete mass slaughter. But rather the commands were meant as warnings that we would be surrounded by very bad influences morally. It would be a priority to avoid them as much as possible. The Torah often uses hyperbole to stress how dangerous something is. Historically we know the Israelites never succeeded completely in removing them.
Some people take the commands against the Canaanites to apply to all non-Jews in the Land of Israel. Yet the Torah allows for non-Jews living amongst us, the Ger Toshav was a non-Jew who had not converted. We are repeatedly commanded to be nice to strangers. And the Mishna in Yadayim declares that since Sennacharib the Assyrian, conquered the territory, all non- Jewish tribes who were re-located were mixed and lost their identities so that it is impossible. Let alone impractical to apply this law nowadays.
And so today, there is much that goes on in the world we live in here and Israel that is bad and morally dangerous. But there are very obvious reasons why we cannot just destroy what we disapprove of. We often have to live with it and find ways of toleration and accommodation. That is why the Torah says the commandments are to help us live, not die by them.
But there is another message here. Ecological factors are important. Degrading land, allowing to go to waste or to be misused are all against Torah principles. We tend to focus only on rituals. But some of the wider, global issues are just as important. We do not live in a vacuum. We have to do our share for the world we live in.