aDSL used to be unbundled, too. And while it was unbundled, speeds were increasing.
aDSL speeds have been pretty flat since they removed the requirement, even though newer DSL technologies are available.
Well, here in Canada they're mostly fiber also -- but it still works. See, for example, https://www.teksavvy.com/ and https://www.start.ca/ ... "TPIA" is what they're called.
In looking them up, I stumbled on mailing lists for TPIAs hosted by Torix. Realised at that point that TPIAs have a lot in common with Canadian IXPs -- both put pressure on prices from Canadian ISPs, TIPAs by consumers and IXPs from businesses/services aghast at how much certain folks charge. See https://cira.ca/sites/default/files/cira-ixp-overview-web.pd... for more on IXPs. I wonder if there's a book on this somewhere, or what ISPs think. Rogers Cable peers with Torix, so it's not exclusively smaller players, in fact I'd say it's the everybody-but-telcos club but I'm sure telcos and US players are welcome if they cared to... (let's pretend they simply are unaware of the ahem, savings...)
Playing devil's advocate here.
How would they increase adsl speed if it's very much distance-related? It tops out at 24Mbps and even then in ideal conditions.
Those newer DSL technologies require laying fiber closer to the customer and that's a nontrivial investment.
Most of that has come from legislation that forced the monopolistic owner of copper wires to let competition use them.
Hence VDSLx is usually rolled out only as part of an FTTC deployment, where the ISP needs to roll out new fibre (rather than copper) to the caninet/junction box, and in most cases install DSLAM units in those cabinets also.