Honestly are the creators of bitcoin core having a laugh?
No.
Mining difficulty will be the reason that mining bitcoins becomes impossible. Why can't it be restricted?
Difficulty means that on average, a miner would need more guesses before a block can be mined. If the Difficulty doesn't change, blocks intervals will become seconds apart and the cap supply wouldn't work. This would also result in a lower network security due to the amount of orphans.
Before all bitcoins have been mined we won't even have the technology to mine them anymore.
Is bitcoins quickly becoming extinct? What would happen if no one can mine a block anymore? Blockchain crash?
Difficulty will adjust. When Bitcoin become extinct, the price would probably skyrocket due to the limited supply in the market. Electrical price is likely to decrease due to renewable energy. If a large miner decides to stop mining, more fees would be paid thus making mining more profitable.