The video was pretty weak.
First off, a bad Bishop, a passive bishop, and a blocked Bishop are not the same thing. For example, if White has pawns on c4, blocked by a black pawns on c5, and a pawn on e4, blocked by a black pawns on e5, and the White Bishop is on d5, this is still a bad bishop. Bishops have 4 classifications. You can have a passive bad Bishop (typical of the French Advance or Classical King's Indian), an Active Bad Bishop (example given above), passive good bishop (i.e. Black's e7-Bishop in the Petroff), and an Active Good Bishop.
The example with the e2 bishop is really weak because white can play f4 immediately. Nobody cares if a mobile pawn blocks the Bishop, you move the pawn with whatever prep may be required to move it. It is all about keeping that pawn immobile, forcing your opponent to maintain a bad Bishop. For example, in the French, there is a reason White pushes e5. To keep that bishop on c8 or d7 bad.
That said, in the exchange French or open tarrasch, that is still black's bad Bishop because of the immobile pawn on d5, but it may be easier for Black to trade off for White's bishop or knight.
Also, the classical development rarely sees both bishops being developed to the 4th or 5th rank. I emphasize rarely.
Far more common is for one of them to go to e2, e3, d3, or d2. Part of it is coordination. The example given there is poor because you will never see a wide open board with bishops on b1 and a1. It is more about coordination, such as going for a kingside attack. Let's say white wants to attack the weak h7 square after black has castles. Bc4 or Bb5 would be stupid and lack coordination with the DSB that went to g5. Instead, you develop them to g5 and d3. The DSB is to rid Black of the defender on f6. The LSB combines with the Queen and either a knight or lifted rook to go for the kill on the black king.
Another common thing completely overlooked here is in Endgames. With a blocked position, bishops that look bad because they are blocked by the opponents pawns are really not bad. If the King's are on the kingside, each side has their LSB, White's is on the other side with his king, and you have something like WP a2, WP b3, WP c4, BP a3, BP b4, BP c5, often times one has to look out for scenarios like ...Bxc4 bxc4 b3 axb3 a2 winning, or if White ignores b3 but can't cover b1 in time, then b2 and b1=Q.
Also, facts about how bishops can indeed influence the other color complex. A knight on a dark square only covers light squares, so a DSB can have major influence over the light squares by pinning or exchanging for a knight.
A lot of weak examples in the video and a lot of missing items. Even the example with the g3 bishop blocked by Black's pawns. White can get that bishop back in the game with f3 and Bf2 (or Be1). He can play h4 to trade on g5 to partially weaken the blockade and open the h-file for attack if his heavies can get there before Black's do. A pawn sacrifice with f4 is possible later on, especially if that scenario is with black only being able to double take on f4 with pawns and is left with isolated double f-pawns.
No follow up analysis of what to do with or against bad bishops. Even an 800 player can see when his bishop is nothing more than a tall pawn. It is what to do in situations with it. In the French, it is often a critical defender to the often weak e6 pawn. There are many other scenarios where it plays a critical role of defending key squares. There is a famous game that I do not recall the players where a superior white Knight on c5 takes a bad Bishop on d7 that shatters black's position completely (covered in Bishop v Knight the Verdict).
There is a lot of editing to do if this is going to be useful to even a 1200 player!
Hello !
To help you identify if your Bishops are good or bad and to give you the keys to turn a bad Bishop into a good one, I have created this video:
Hope you will find it useful
Do not hesitate to ping me in case something is unclear or if I forgot to deal with one part of the issue.