To compare our bullet points for maglev and high speed & conventional rail:

• there’s a big step in price between “a railway line built to millimetre precision” and “a completely new type of infrastructure that may or may not need superconductors to work”
• there are way more manufacturers for components of high speed rail. For rolling stock there 4 in Europe alone, plus more in Japan, South Korea and China. As for signalling, it depends on the underlying tech. And if we follow the current European tech standard, that encompasses a standard… That is made by multiple manufacturers, and where their systems are operationally compatible.
• for one, high speed rail is still rail, so building at grade & laying them on the ground is trivial compared to maglev systems. While some maglev technologies must be built like a bit of a monorail, which must be built elevated everywhere. And if we step outside of high speed rail, and point to rail in general, the mere existence of level crossings and street running disproves the fact it can only be built grade-separate. Sure, level crossings for HSR are a reason for the planning engineer to get fired, but for rail in general, it can happen.
• this depends on what is already there. Most high speed trains use standard gauge, and those that don’t, use broad gauge, and for that, only the Russian Sapsan comes to mind. If your country has standard gauge track, you can use the existing railway lines into town, disproving your point. And as for signalling, you can fit a train with multiple train protection systems, and many places are instead working towards using high speed signalling for general use, since the tech that makes high speed trains go BRR is the same tech that allows regular trains to run closer together. Finally, electrically, many countries use the same power on the wires on their high speed network as their general network.
• I’ve seen footage* of a set of switch points with a diverging speed of 160 km/h, and it needs 9 switch motors to work. Proper high speed switches need even more, last time I checked the adopted standard was diverging speeds of 220 km/h. However, these motors all work in parallel, so the difference in switching time is negligible compared to a more basic type for general use. And these points work by bending one rail a little bit out of the way, bending another rail into place, and for high speed, pushing the frog (image for clarity) to the other side. This all unlike maglev, where you need to invasively rearrange the whole track, the replacement of which is probably several metres away.

High speed rail has enough compatibilities with regular rail to make sense.

EDIT: *this video pretty much starts out with footage of the switch points in question.
Also, you may see yellow tiles in the middle of the tracks, those are Eurobalises, European standard beacons for ETCS signalling, which is the current standard for train protection for new high speed lines in the EU, as well as general train protection in Luxembourg and Switzerland. The track in the vid is one of a few places in that country where the system is already in place on a regular mainline, though it’s not yet in general use for regular domestic trains out there. That’ll be another few years into the future.