Yes, agriculture can lead to mass deforestation - unless a society industrializes, and thereby reduces the pressures that strip timber from the land for heating and cooking fuel. Again, INDUSTRIALIZATION reduced the economic returns of slavery to the point where it was no longer viable. It is widely suspected that "alcohol and drugs" (the former is also the latter, by the way) existed in pre-agricultural times, although there is obviously no written history to support this claim (WRITING being another one of those wacky technological benefits). Even so, I'd say your claim that alcohol and drugs are unmitigated evils is debatable, at the very least.
Climate change / ecological damage happened even prior to the development of modern economies; you won't find giant ground sloths or mastodons roaming North America - they were hunted to extinction thousands of years before Europe discovered the New World.
Over-population is a claim about the carrying-capacity of the world, and technology raises the carrying capacity, so again, I really must disagree.
Hunter gatherer / subsistence farmer societies are not without impact. And no, they were for damn sure not better off than we are now. It's nice that you have the leisure time to daydream about the noble savage, but understand that had you been born at that level of technology, you'd more likely than not be dead several times over before reaching your current age, let alone doing so with your level of nutrition and relative dearth of crippling childhood diseases.
Yes, technology HAS made us better off. Indeed, I will go further than that - it is the most powerful, if not ONLY, way of doing so.