I haven't played New Leaf at all since New Horizons came out, but I don't feel like NL is obsolete at all. There's still plenty of people who havent moved on to NH yet, for various reasons:
- People who can't afford a Switch/can't get one because of the current situation
- People who live with others who also play Animal Crossing, but can't afford multiple Switches so they can have separate islands
- People who want to play with others but can't afford/don't want to get NSO
- People who don't like the changes made in NH, like the crafting system and tools that break after a certain amount of uses
- People who prefer to play the older games over NH for various reasons - nostalgia, the older ones having a different 'feel' to them, etc.
There's probably a whole bunch of other reasons I haven't listed, but these are a few I can think of. Because there's so many reasons to still play NL, or any of the past AC games really, I don't feel like NL has become obsolete with the release of NH.
I am aware of most of the situations you mentioned. I'm sure New Leaf is still played by many people as I am currently still playing it. However, I believe what others have mentioned is the reality for old games and consoles:
1. Many players gravitate to older titles like Animal Crossing Wild World for the feels and nostalgia (from what I know about more passionate Animal Crossing fans).
2. Animal Crossing New Leaf will still be playable but many online features will be inaccessible when Nintendo shuts down the wifi connection (Dream suites, Club Tortimer, etc). Similar to what happened to older AC titles.
3. I was merely hoping the potential future updates would be in the form of more Welcome Amiibo updates which is possible since the changes will be small but it is up to the AC team. However, with the AC team focusing on making New Horizons better in the future, it is highly unlikely.
4. Nintendo Switch Lite is very affordable compared to the original Nintendo Switch and future models could be even cheaper if Nintendo wants them to be. Kids nowadays wants the latest gadgets and games.
5. The New Nintendo 3DS and Nintendo 2DS has been discontinued, once the parts runs out, it will be harder to get a refurbished one or even maintain them (The 2DS XL is the only model left to still be in production). Without the 3D feature, New Leaf will pale in comparison to New Horizons.
6. New Horizons was made possible by New Leaf, Pocket Camp and Happy Home Designer. Many players have voiced their disappointment with the PWP system and not being able to control villagers housing plots.
People have said that as long as there is a community, Animal Crossing games will not be obsolete, but Nintendo will no longer support those older titles in terms of updates and maintenance. It's already a blessing that the 2DS & 3DS consoles and games have last for more than a decade.
All these are based on observations and what has already been mentioned in this forum.
No conflict intended, I too hope New Leaf lives on for a little while longer
