Spoilers for Doomsday Clock (2018-2020), Final Crisis: Legion Of Three Worlds (2008-2009) and various other comics.
The Legion of Super-Heroes are a fictional team of super heroes that usually appear in stories set 1,000 years ahead of present day DC Universe stories. Their first appearance is in the anthology series Adventure Comics #247 (1958), specifically as guest-stars to the feature character Superboy (Clark Kent). They have since gone on to become stars in their own series Legion Of Super-Heroes [2019-Present], and certain other titles (such as Final Crisis: Legion of Three Worlds). There are many positive aspects of the Legion Of Super-Heroes including: A great concept, iconic stories by notable creative teams (such as Legion Of Super-Heroes: The Great Darkness Saga (2000) writer Paul Levitz and artist Keith Giffen), and their various series usually promise hopeful futures. However, various reboots have made which version is the canonical Legion a confusing mess.
The initial rebooting of the Legion comes about due to the series Crisis on Infinite Earths (1985-1986) and Man Of Steel (1986) removing Superboy (Clark Kent) from canon. While this change does not affect a vast majority of DC’s characters post this first crisis, rebooting most of them the Legion is left with a conundrum due to not getting a reboot. So a few retcons occur around the late 1980s and early 1990s where the Legion’s Superboy is actually from a pocket universe, and later is a version of another character Mon-El/Valor (Legion of Super-Heroes #38  and Legion of Super-Heroes Annual #2 ). Yet, these are just the earliest in a long line of retcons that plague the fictional team’s publishing history (See comic historian Michael Kooiman’s website cosmic teams for more details on these retcons). However, the mini-series Final Crisis: Legion of Three Worlds is arguably the smartest retcon due to how it uses the multiverse to make all versions possible. This happens in the story via a team-up explaining how time travel can also result in traveling to a parallel earth. The primary example they give in-story is Supergirl’s time with the Legion Of Super-Heroes from Earth-Prime.
However, confusion is restarting due to the comic storyline known as Doomsday Clock. This is mainly due to Doomsday Clock introducing a new iteration of the Legion of Super-Heroes that supplants the primary Legion that Final Crisis: Legion of Three Worlds features. Thus, the explanation given that all Legions are relevant due to the multiverse is seemingly no longer true. One also has to consider the fact that problems such as climate change and COVID-19 in our world are causing possible far-flung future stories to feel a bit unlikely. In other words the concept of future heroes is not as believable as it should be. Thus it is somewhat hard to justify them being set later and later in DC’s timeline with each new reboot. Not to mention that if creators have to view things from a punk (no future) type mindset than the series will (arguably) be harder to create.
Yet this does not mean Legion of Super-Heroes should not be published. Rather it means that DC’s staff and freelancers should implement a few of the following ideas: No more reboots for 25 or fifty years. If that first idea is too restrictive then at least say that all versions are relevant and have a throwaway line reminding readers every now and then. Lastly mention that referencing ways to prevent climate change in any future story arcs, especially ones featuring ‘present’ day characters (such as Jonathan Samuel Kent/Superboy), could provide ideas that readers might be able to apply in reality. In conclusion the Legion is still a great concept and hopefully one that readers will see a consistent fictional history for someday.