One big challenge is that the idea of a virus being "alive" is a touchy subject. The vote is still out but I'm in the "No, they are not" camp, viruses are just clumps of organic molecules that are like a mouse trap, they spring into an action when triggered, but they aren't "choosing" to trigger.

Most antibiotics don't kill bacteria, they either weaken them or slow their reproduction rate so that our immune system can step up and wipe them out. 95% of the time, our immune systems are the real hero, not the antibiotics. Additionally bacteria are "external" to our cells, so we can find them and attack them easier.

Viruses invade our cells and do their damage inside, so passing immune system cells can't see them or engage them because they are hiding. Again, if our goal is to just mess with the invader until our immune system can neutralize them all, if our immune system isn't taking because the viruses are hiding, that strategy doesn't really work.

Finally, viruses change insanely quickly, they are like the Borg if you're a Star Trek person. The virus a person get's infected with is often not the virus they infect other people with because they are constantly changing and evolving. Just look at how many strains and variants of COVID we have already, how the treatment and symptoms keep changing as well.

I bet I'll get some heat from the "are viruses alive" comment, and we can all agree that the concept of "life" is really, really complicated if you spend a few minutes thinking about it. For any hard "life needs X" line you can draw, you'll find a clearly living animal that doesn't need that. At the least, I draw the line on metabolism for viruses, they do not require, use, ingest, or produce and sort of energy required to grow, move, reproduce... you know, live. They are just molecular bear traps waiting for the right cell to step in and produce more bear traps.

A bacteria has a lot of stuff that it needs to do in order to remain alive.
It tends to do that stuff differently from how our cells do it.
So if you stop that stuff from happening, the bacteria dies.

A virus on the other hand is arguably not even alive. A virus does so few things on it's own that many scientists seriously say that we shouldn't call that small chunk of genetic material wrapped in protein "life". It is very hard to kill something that isn't even alive.

The medicine we do have concentrates on sticking to the virus or the sticking to the places the virus sticks to so it can't get in.
Targeting the stuff that makes copies of it self doesn't work well because our cells need that to remain alive.

Killing pathogens is actually really easy. Some alcohol, bleach, or plain old fire will do the trick - the hard part is killing pathogens without hurting the infected person.

In order to kill a pathogen without hurting the infected person, you need to aim for something that the pathogen has but humans doesn't. With bacteria, there is an easy answer - cell walls. All bacteria have cell walls, and human cells do not, so most antibiotics target cell walls in some way (usually stopping bacteria from producing more cell walls, which stops them from dividing).

Viruses don't have a single common trait that's easy to target in that way. In addition, viruses don't spend most of their life cycle moving around independently like bacteria do - viruses will inject their DNA/RNA into a cell, and then that cell will be making more viruses. Finally, viruses are much simpler than bacteria, making them harder to "kill" without completely destroying them - which is harder to do without causing collateral damage.

Because they are almost like organisms with DNA. You are also an organism with DNA, it is hard to make something that would kill them and not you.

(This is according to my knowledge on the topic. Might be wrong. If so,please correct me).

The challenge is that viruses use the host's own cells to multiply.

A virus outside the body can be dispatched with soap and water, or alcohol, but once it's inside you, it is literally inside your cells.

So anything that works well against viruses are probably going to interrupt essential cellular functions for you too.

Antivirals do work for the viruses they are designed to treat. HIV drugs have completely turned the tide against that disease and Paxlovid is 90% effective in preventing hospitalization and death from COVID. These drugs work work very well so I reject the entire premise of this question.