It's producing much less oil than it would have been without these strikes. At the minimum, it's costing Russia a lot of money, and defensive wars are won by making it too expensive for the invaders to keep going.

Russia had a lot of oil infrastructure. Some equipment can take months or even years to manufacture. Its routine to keep lots of spare parts around if possible for critical or routine repairs. Down-time on the plant = losing lots of money.

So the initial strikes were an inconvenience and caused a short pause in production. Russia rapidly repaired the damage infrastructure with spare parts.

Then Ukraine keeps hitting the fully operational facilities. Russia utilizes more spare parts and they start to run out. This delays the recovery times as reconstruction waits on parts to be manufactured. This also delays normal maintenance, leading to more breakdowns across the entire system.

Currently it's reported that production across the entire system is down. If Ukraine keeps hitting a fully functional facilities regularly, the production will remain suppressed for years.

They can always buy more oil from India.