I think the complexity lies in the fact that if you keep trading the same stock the wash sale thing goes into a perpetual cycle.
For example, if you traded 200 shares of stock syz (trade #1) and took a loss, say from $10/share to $8/share to a total loss of $400. In the next 30 days you traded xyz again for 100 shares (trade #2) in a winning trade. Now the half (100 shares) of the original 200 shares trade (#1) became a wash sale and the $200 loss is disallowed in the original trade. Instead, it is now part of the second 100 shares trade’s (#2) cost basis.
If during the 30 days you traded xyz once more in 50 shares (trade#3) and took a loss. Now 50 shares of the original 200 shares trade (#1) became a wash sale and the $100 loss is disallowed in the original trade and added to the cost basis of the 50 shares trade (#3). However, if within 30 days of the 3rd 50 shares trade (#3) you traded xyz again for 100 shares (trade #4). Then the 3rd 50 shares trade (#3) became a wash sale and its loss plus the $100 loss from the original 200 shares trade (#1) is disallowed again, which will be added to the cost basis of the last 100 shares of the xyz trade (#4). If the last 100 shares trade (#4) is a winning trade all is good. But if it’s a losing trade any future xyz trade within next 30 days will trigger a wash sale of that 100 shares trade (#4).
You can see this wash sale cycle goes in perpetuity as long as you keep trading xyz and have losing trades. Wash sale rule only applies to losing trades. I am sure brokers use a software to do this wash sale calculations throughout the year.
The only way to clear disallowed losses from previous wash sales is to stop trading the same stock for 30 days after a loss (or make sure you only have winning trades within 30 days of the last losing trade

), after which you start fresh again. You cannot clear previous wash sales but they don’t matter either. The disallowed losses matter.