The first washout (or tie) is almost as good as a win (unless its against the bottom side). The second is as good as a loss. Sri Lanka has had two washouts.
The second one is worse than a loss, as it turns the net effect of both matches into a loss.
This was a factor in working out how Australia was guaranteed qualification by winning last night. It's still possible for 3rd-4th-5th to be Australia, England and Sri Lanka all tied on 12 points. The first tie-breaker is the number of wins so Sri Lanka's two washouts are as good as a loss.
Effective win percentage (i.e. discarding No Result points) would be a better first tie-breaker, as that scenario would give Sri Lanka 3rd place on 71% (5 wins from 7 matches) compared to Australia and England on 67% (6 wins from 9 matches).
Why couldn't they extend those matches where the D/L method is currently used? Especially where they reduce by a match by less than ten overs in the second innings. Surely an extra hour of time would be more even for both teams than the abstract that is the D/L handicap.
They already do extend the finish time of the match.
DLS (Duckworth-Lewis-Stern, after D&L handed the system over to Steven Stern who had assisted them with previous updates) only comes into play once the additional time is completely used up.
The standard additional time allowed for an ODI match is one hour, but allowing for even later finishes in the Event Playing Conditions is permissible.
Fair play to the CWC19 organisers, they have made some level of mitigation for British weather by allowing more extra time than the hour minimum. The finishing times of matches with reduced overs so far have been:
+89 minutes for Afghanistan v Sri Lanka (scheduled to use around +120 minutes, but both teams got bowled out)
+90 minutes was scheduled for South Africa v Afghanistan, but neither team used all their overs
+88 minutes for India v Pakistan
+119 minutes for New Zealand vs South Africa last week
If there is a substantial rain delay late in the first innings, there is also the option of reducing the time loss by taking the lunch/dinner break during the rain delay and having a 10 minute changeover at the end of the innings. This might have been considered at the Australia v Bangladesh match last week if the rain at the end of the 49th over had lasted longer.
The most ridiculous is using D/L for 20/20 matches - just play the match out, obviously the weather has cleared.
T20 matches do have extra time allowed for, but less than 50 over matches.
The most common use of DLS in T20 matches is to determine the result when no further play is possible and the match result has to be called. You can't keep people waiting around forever!
In a longer tournament like the BBL where teams play at home and away, holding a double-header on the return fixture should be considered as an alternative to calling off the first fixture between the teams.
Spectators just want an equal footing for both teams.
I think the DLS batting resource curves are about right. India were well on top in their match against Pakistan and that was a fair result.
If there's a substantial delay quite early in the first innings which eats up all the extra time and loses a lot of time, then a better method than DLS might be to completely scrap the play up to that point and hold a fresh match of (for example) 25 overs each. Put the side which was fielding in to bat first (to fairly manage the workload on their bowlers) and allow the sides to submit a fresh team sheet.