Problem is, there is no "One Size Fits All System". You have to study and UNDERSTAND, NOT MEMORIZE, the moves you are playing. Even the London System and Hippopotamus are not one-size-fits-all openings.
London:
Great - When Black has played a very early ...d5, like move 1 or 2 or 3.
Ok - Against Nimzo, QID, and KID type setups
Dubious - Against Dutch setups
Borderline bad - Against the Modern Defense
As far s the Hippo, like the Classical or Stonewall Dutch, it should be a last resort, not a pre-meditated Defense. For example, in lines of the Modern Defense with 4...a6, like 1.e4 g6 2.d4 Bg7 3.Nc3 d6 4.Nf3 a6, Black's goal should be to play ...b5, ...Bb7, ...c5, etc. He should ONLY play ...b6 and the Hippo Against 5.a4, to avoid a backwards b-pawn after a5 by White. Against the Austrian Attack, Black must act fast. Playing the Hippo against the Austrian Attack you might as well resign on move 4.
Others that people try to use as "Systems" just don't work.
Torre Attack - Works well against Nf6/e6 and Nf6/g6, fails against 1...d5 or 1...Nf6/2...d5.
Colle System - Works when Black has Blocked in his light-squared Bishop (d5/e6/Nf6 or Nf6/e6/b6, etc) If the Bishop comes outside the pawn chain, known as the Anti-Colle, White must play c4 and allow the Slow Slav (1.d4 Nf6 2.Nf3 d5 3.e3 Bf5 4.c4 c6 is the same as 1.d4 d5 2.c4 c6 3.Nf3 Nf6 4.e3 Bf5).
English Opening - This should NEVER be played systematically. Some thing you can close your eyes, play c4, g3, Bg2, Nc3, and then open your eyes. Others thing the c4/e4 setups are automatic. The c4/e4 lines should only be played when Black has both played ...e5 and Fianchettoed the Bishop, like Reverse Closed Sicilian positions. After 1.c4 e5 2.g3 Nc6, WHITE MUST PLAY 3.Nc3! Even Marin mentions that any time Black plays ...Nc6, always answer with Nc3. Why? Here's one big reason: 1.c4 e5 2.g3 Nc6 3.Nc3 f5 4.Nf3! Nf6 and now the only good move is 5.d4, when 5...e4 should be answered with 6.Nh4 (Stronger than 6.Ng5), threatening f5, and after say, 6...d6, Black can play ...g5 at some point. Now we see why 3.Bg2? is a bad move against 2...Nc6. The knight would be trapped. Here, we develop the Bishop classically to e2 or d3, move the Knight to g2 whenever ...g5 comes, and then play h4, looking to entice ...gxh4 or ...g4, both of which give White an excellent permanent outpost for the knight on f4. So once again, playing systematically like a blind squirrel will fail you.
Other Openings that people try to play systematically that just don't work are:
Catalan- Only works when Black's LSB is behind the pawn chain.
Kings Indian Attack - Again, like the Colle and Catalan, only effective when Black's LSB is behind the pawn chain. KIA vs French and KIA vs 2...e6-Sicilian can be effective, but against most other defenses, it's not.
Therefore, you need to find an effective combination of openings and not rely on a single "System". Some examples:
Trompowsky/London -Tromp against Nf6, London against d5
Torre/London - Torre against Nf6/e6 and Nf6/g6, London against d5 or Nf6/d5
Torre/Colle/Slow Slav - Torre against Nf6/g6, Torre or Colle against Nf6/e6, Colle against d5/e6 or Nf6/d5/e6, Slav with 4.c4 against Nf6/d5/Bf5 or Bg4.
There are other combinations, but there is no such thing as a one size fits all. In fact, those 3 examples given above, I play the first combo now. I played the third combo in 2019 before COVID.
And just as additional info, I said "Just like the Stonewall and Classical Dutch, it should be a last resort", many Dutch players don't seem to understand that the Stonewall and Classical should not be your first goal. Your first goal should be that poor Bishop staring at pawns on d7, e6, and f5. The Stonewall and Classical are a last resort. After 1.d4 e6 2.c4 f5 3.Nc3 Nf6 4.Nf3 - where the Knights can no longer connect like the do if the knight goes to e2, then 4...Bb4!, playing like a Nimzo-Indian. If instead 4.e3 or 4.Bg5, then 4...b6!!. Black can bring his Bishop to life by Fianchettoing it. This is why White should Fianchetto the light-squared Bishop, playing g3 either on move 3 or 4 (or move 2 if 1...f5). Beat Black to the long diagonal. It is HERE that Black resorts to either the Stonewall Dutch (4...d5 with ...Bd6 and ...c6 coming in some order) or the Classical Dutch (4...Be7, 5...O-O, and 6...d6).
Good evening. I have read a great deal about the London system, and the hippopotamus system. As I understand, they seek positions that are not overly sensitive to what your opponent is doing in his/her opening. What are the other systems that do not require memorization of numerous lines. I just want to get to the middle game and look for opportunities. Thanks in advance.