In my opinion, these were the eras:
-> 2012: professionalization era: when some players were still playing competitive in CS 1.6, and then were migrating to CSGO later with updates for better gameplay
-> 2013-2015: Swedish era: NiP and fnatic dominating the scene with multiple titles and majors
-> 2016/2017: All-americas era: With the rise and popularity of CSGO in the americas due to the influence of pro players like FalleN, n0thing and others, the teams from the american continent started to get more competitive and to play equally (for the first time in CSGO era) with EU teams. Luminosity/SK, Cloud9, Liquid, CLG and Immortals were amongst the best teams in the world in that era. SK won 2 majors in a row and in the next year Immortals were vice-champions in Krakow. Later on 2018, C9 won the Boston Major Finals against FaZe, being one of the best major finals in the history, if not the best.
-> 2017 - 2020: Astralis and EU superteams era: Giant organizations like FaZe, mouz and G2 spending a lot of money building superteams with the best players from their regions, being G2 a french superteam, and, FaZe and mouz being EU superteams, and together with the rise and popularity of those teams, Astralis became the team with the most CSGO major titles in the world, with the same core since TSM.
-> 2020... : CIS era: CIS region teams rising in the scene with young teams and prospect players with a lot of potential, teams like Spirit, Avangar/VP, Nemiga, Na'Vi, Gambit and Winstrike being the most notable teams always making presence in the most important championships and with the most notable players, like s1mple, degster, sh1ro, electronic, Hobbit, Boombl4, YEKINDAR etc.