I really don't think they are. If I follow the link in your signature bar, for example, I see two entries from 20th and 22nd July that show classic examples of cycle lanes that I wouldn't want to use, and that are likely to cause me to get problems from motorists when I don't use them:
That one would require me to cycle in the door-opening zone of the parked cars. There is no way I would cycle in it unless the parking bays were all empty. If I went to the left of the little island, I would have to swerve suddenly out into the carriageway to get out of the door zone, when I should really be moving out well in advance, so I would probably go on the outside of that island.
In that one, with the traffic as shown, I would want to be in the centre of the lane with the oncoming truck there and the side road to the left. The cycle lane goes across the mouth of the side road, and I would be outside of it when passing that side road in any circumstances. The door opening zone of the parked cars extends to the solid white line of the cycle lane, so I would be outside of the cycle lane there, and I would be taking the centre of the lane in the approach to the pedestrian refuge, given the pavement extension that immediately precedes it.
I would expect to get drivers regularly blasting their horns behind me and pointing to the bad cycle lane in both these cases, which really does make the journey rather unpleasant.
Something is not better than nothing when it causes these problems.