No they are not. They only work well at small percentage of generation when you have enough hydropower backup (effectively, batteries): generate from solar during day, and generate from hydro at night (or use fossil fuel backup).
> solar
In California large amount of electricity is consumed by air conditioners (4%). And they work very well together: on hot days you need more electricity for air conditioners, and on hot days solar generation works better.
And you need more air conditioners during summer, and solar works better during summer.
The opposite is true in Ukraine. They don't need air conditioners because summers are not too hot, but but they need to heat buildings at winter because winters are very cold (when solar is very poor) especially at nights (when solar does not exist).
> wind
You cannot place wind turbines anywhere. You need a place with a constant high wind (that's why offsore farms work better). I guess there are no such places in Ukraine. And still you need to have a hydro or fossil fuel backup, because wind itself cannot produce electricity constantly.
> cheapest sources of energy available today
They are cheapest because they are subsidised on one hand, and on the other hand, nuclear is penalized by lawsuits and regulartions and inspections (in the US; in Ukraine the economy barely grows, they don't build much new power plants).