Agreed. Our system under Pep tends to change every 2/3 seasons because, eventually, teams work us out and Pep has to try something different to keep us a step ahead. It was what made Ferguson so great, just keeping that door revolving often enough that they were never off the top for long. He always played 4-4-2 but he always opted for a slightly different version every 3/4 years to avoid things going stale. In 1999 their system was a traditional 4-4-2 (Schmeichel; Neville, Stam, Jonsen, Irwin; Beckham, Scholes, Keane, Giggs; Cole, Yorke), but by 2003 they'd moved to a system that prioritised ball retention just that bit more (Barthez; Neville, Ferdinand, O'Shea, Neville; Beckham, Veron, Scholes, Giggs; Solskjaer, Van Nistelrooy). Then when Mourinho knocked them out of the Champions League, came to Chelsea, and brought something new to the league, Ferguson adapted again by opting for a slightly skewed 4-3-3 in 2008 (Van Der Sar; Brown, Ferdinand, Vidic, Evra; Carrick, Scholes, Giggs; Ronaldo, Rooney, Tevez). By the time Ferguson left, United were playing stodgy football but it was effective because it was a solid 4-4-1-1 that was calm in the middle and ruthless up front (De Gea; Rafael, Ferdinand, Evans, Evra; Valencia, Carrick, Giggs, Young; Rooney; Van Persie).
In Pep's first season here, he used what Pellegrini had left behind and took a hit for one year in order to teach the players his system. Then in our Centurions season we prioritised taking advantage of transitions with fast, wide wing play and a lot of bluster (Ederon; Walker, Otamendi, Stones, Delph; Fernandinho, De Bruyne, Silva; Sterling, Aguero, Sane). But that system left us a bit exposed in tight games, so in 18/19 he shored us up and played a slightly more detailed, slower game with Sane on the bench more often (Ederson; Walker, Otamendi, Laporte, Zinchenko; Fernandinho, Bernardo, Silva; Mahrez, Aguero, Sterling). Then when Kompany left and Fernandinho slowed down, we got a bit found out quite a bit. Miles behind Liverpool in 2020, in a terrible run of form at the start of the 2020/21 season, Pep made his most radical change yet by opting against using a striker, going for maximum ball retention and control, and trying to win games via slow strangulation (Ederson; Walker, Dias, Stones, Cancelo; Rodri, De Bruyne, Gundogan; Mahrez, Bernardo, Foden). Sooner or later, this strikerless system will get found out and he'll adapt again - hence why we're bringing one in over the summer. It'll be fun to see where we go next.