It’s still fairly popular, but the statistics show that X usage is gradually declining. Elon claims that X is more popular than ever, but the platform doesn’t publicly release its own stats, and publicly available stats say otherwise.
If you like AI and tech, there are some pretty thriving sub-communities. AI stuff, and a lot of tech stuff happens on X first. Claudebot/OpenClaw/Hermes all began on X months before I commonly saw them appear on other platforms.