The usual answer I've found to this question is Microtik, they strike a similar balance between enterprise feature-set and more consumer level price point as Ubiquiti sort of aims for with the Unifi line.

The quality/feature set is there and the software is well designed, even if not quite as networking beginner-friendly as Unifi has become. Mikrotik's RouterOS can do much the same tasks as Unifi's management console, and can configure for auto-adoption of APs/other hardware in the Mikrotik range just like Unifi does for their own hardware.

Most competitors (I see Aruba suggested) are priced much more into the enterprise/business buyer realm. Unifi has generally been keenly priced in this market, their latest Wifi 6 APs are just 99 dollars each (when in stock of course...). Microtik's pricing is generally comparable or cheaper than Unifi in my experience.

https://mikrotik.com/

Secondhand Ruckus APs are a pretty decent alternative, you'll have a hard time getting AX gear for a reasonable price though.

edit: Secondhand Ruckus/Brocade switches are solid, at least on the 7000 series the evaluation key has no time limit so you're not license-limited in what you can do with them. Switches are mostly <$250 on eBay if you're buying an ICX7150, ICX7250, etc. Yes, that includes PoE models.

That’s the real question. Aruba has some relevant offerings, but UniFi is still pretty unique in what it offers to prosumers.

Seems like a market opportunity!

Is it just software that's UniFi's weakness? Anything wrong with the hardware itself? I've had quite good luck with UniFi in my home myself but perhaps I'm not using all the features...