As a long-long-time Lego fan, yeah, some of us will buy the 'knockoffs' if they provide something different that Lego itself wont.

I myself have tried many of the non-Lego lego sets over the years. One that has been holding my attention recently has been Lumibricks, which integrates lights into the sets, and is also cheaper than official Lego sets for similar part counts. One of the big things I've found is that where Lego wins a lot of points is on their instructions and build steps. Many other companies either make their instructions hard to read or parse, or don't do a good job with progressively building up subassemblies so they don't collapse in your hands. But there are some Chinese companies that are now making the entire experience a similar quality level as Lego does. A lot of the 'knockoffs' also focus more on the visual of the model rather than the play. Lego itself is often willing to sacrifice some realism to make sets be more playable, much to the chagrin of some fans.

Lego used to have a huge moat in manufacturing. They made good molds, they perfected the processes for making pieces (barring a few problematic colours....cough brown and dark red) and they invested heavily into clear design targeted towards accomplishing a certain level of play and excitement from those buying and building the Lego sets. Now though, those things are not a moat, they're just basic table stakes, and there are a lot of other new players entering the market who are doing just as good. I've seen multiple stages of Lego's evolution over my life, and I think they're going to need to come up with something new that's not just a silly expensive noise/light brick to continue to command the price premium that they do. Sure, their IP deals will probably float them for a while, but without bringing something new to the recipe, they might slowly start to go the way of jello deserts.