IMO, the biggest drawback with Bitcoin is the high transaction fee and delays in getting confirmation. For example, with PayPal the fee is fixed and can be as low as $0.30. However, the transaction fee for Bitcoin is very volatile and it can vary from anywhere between $1 and $20 per transaction (depending on the congestion in the Blockchain network).
Also, PayPal transactions get confirmed within a few seconds (the same with Visa or Mastercard as well), and they have the ability to handle millions of transactions every hour. On the other hand, with Bitcoin you need to wait 10 minutes to 60 minutes to get the first confirmation. And even with the recent increase in block size, it may not be able to handle more than 10,000 transactions per hour.
Exactly. In Bitcoin's current state, we'll experience the inconvenience of high transaction fees and slow confirmation times. Luckily, the Lightning Network is being heavily tested in order to make cheap, instant transactions a reality. Only then, Bitcoin will be able to compete with the likes of PayPal, Visa, and other traditional payment processors. Of course, the Lightning Network might not be the perfect solution for scaling (since it'll reach its peak capacity at some point) but it can be improved over time. The Lightning Network with a slight increase in block size would allow Bitcoin to remain scalable and secure enough for the mainstream world to use.
Still though, Bitcoin is still much cheaper and faster than wire transfers. While sending a payment through a Bank may take days, Bitcoin's transactions settles within a few hours (depending on network congestion). Despite this, Bitcoin and traditional payment processors will part their separate ways as they're distinct from one another. Bitcoin will continue to be prominent in the decentralized world, while traditional payment processors will be the norm in centralized finance. This is true, since payment processors use Fiat as their underlying currency. And Fiat is still largely dominant within the mainstream world.
Nonetheless, time will tell us how both camps (Bitcoin vs traditional payment processors) will advance within the mainstream world. As long as people continue to use them for daily payments, they'll be here to stay for a long time. Just my opinion