Of course people care about the tradeoffs of fossil fuel consumption. If they didn't we wouldn't be in the position we are. However:

(1) Even ignoring global warming, fossil fuels are a large but ultimately limited source of free energy; if we wait until they run out or get too expensive before transitioning to a more sustainable energy grid, we may not be able to make the transition at all. If we do not restrict prices artificially, we are just delaying the inevitable; after the prices go up enough, fossil fuels won't be profitable to extract and we will more or less be out. We had better be ready for that moment.

(2) There's no reason to think that the Earth's feedback systems will kick in in time to prevent major damage to the Earth's ecosystem (including a mass extinction event, the acidification of the oceans leading to the destruction of large amounts of the planet's biome, and the desertification of much of the Earth's habitable land). If it happens (as seems likely to at least some extent, since by many accounts it's already started), it won't even be the first time that chemical changes to the atmosphere due to living organisms caused something like that. People aren't worried (for the most part) about a Venus scenario, they're worried about making the planet far less hospitable to humans and displacing or killing billions of people.

(3) (Almost) nobody is suggesting we return to a pre-industrial agrarian economy; that's a total strawman. People are saying that what's happening right now (an increase in fossil fuel usage) is totally insane. In order to even have a chance of avoiding some of the effects from (2), we (especially first-world countries) need to be making dramatic cuts in fossil fuel usage, and investing a large portion of our GDP into building infrastructure for renewables--particularly large-scale storage which makes wholesale replacement of fossil fuel power plants feasible without forcing us to give up 24-7 power. The fact that we have fossil fuels available right now (particularly oil) makes large-scale construction tasks like this far easier than it would be if we wait. Instead, people (including you) are arguing against any disincentives whatsoever for wasting them on trivial things like energy production.

(4) For new power in developing countries without the expectation of continuous access to electricity, renewables (particularly solar) are already the cheaper option even without subsidies, with solar in particular representing most new growth in electricity consumption in those countries in recent years. On the flip side, developing countries and the poor (especially developing countries in hot climates) are going to be among those hurt the most by both warming temperatures and increasing energy prices; people without access to consistent power, air conditioners, or proper ventilation will have little choice but to migrate. Moreover, the existing dependence on fossil fuels in those countries often makes them beholden to one or more wealthy "benefactors", which can exploit them to extract essentially whatever economic or legal concessions they want. Most of those countries (especially those in Africa, which has plentiful sunlight and will be among the worst-hurt continents by warming temperatures) will benefit far more from joint investment in renewable infrastructure than they will from relying on coal, gas, and oil shipments from other countries, especially when they become scarce.

I don't think fossil fuels are evil. I don't even think fossil fuel companies are evil (entirely, anyway). But we have to stop living in a fantasy world where we have unlimited resources, can always defer action until it's "naturally" economically profitable, and the effects of each country's decisions can remain isolated to that country. If you really believe that modern energized life is great (and I do), our current strategy of clinging to our current energy infrastructure and energy consumption habits until it's too late doesn't make any sense.