I don't think it was ever wise to keep both sides of the river warded even when green wards did exists...
You should buy a pink and place it depending on your play style, always making sure to favor that side of your lane so you can duck into the river/jungle in the event of a gank from the unwarded side. If youre an aggressive player that will be shoving the wave, a good spot for it would be the bush behind your enemies red buff so you can see them come really early. Another good aggressive spot is in the bush in between the closest jungle entraces, but this is pretty well known for having a pink in it so I doubt itd last long. The last place for a ward, especially if youre going to just be last hitting/ letting your opponent push is in the bush on the edge of river that extends into your friendly side of the jungle. This placement is more defensive in nature and if someone wants to clear it they have to put themselves in a somewhat vulnerable position to do so.
To compliment your pink ward, you should utilize your trinket ward whenever you change your playstyle (going from passive farming to pushing the wave, for instance) or to get some deep vision in the enemy jungle during an invade/enemy jungle route gank to keep an eye out for their jungler.
The key is to place your pink ward in such a way that you never provide an easy gank opportunity to your opponents, forcing them to take less desirable paths to try to get to you than they otherwise would need to, opening them up for counter ganks or at the very least wasted time/resources. A key element of having less vision but still being safe in lane is understanding that when a gank occurs taking a straight path back to your tower isn't always the best choice. Having one side of the river warded means that you will know with certainty that it is reasonably safe for you to go there to avoid death or at the very least buy time for your own jungler/teammate(s) to come lend a hand.
This is made easier by the fact that pinks cost the same amount of gold that greens used to.