I’ve been there on tour once, and I just looked at an online map to make sure I didn’t misremember. I also follow a guy on YouTube that talks about geology and has been focused on Iceland lately, so I think that makes me a complete expert.

Joking aside, the road to Grindavik is sort of out of the way, but it is the connector road between the south coast and the airport, so it’s like a 45 minute diversion to get to the airport from the south coast (and vice versa). And like an hour+ diversion if you’re going from the south coast to the Blue Lagoon/the geothermal power/hot water plant that provides power and heat to the airport and (I think) most of Reykjavik.
Unfortunately the power plant/Blue Lagoon is very close to the fissure, and it’s possible a future larger lava flow could damage them. (It is expected more fissures/flows will occur, but the location and size are unknown.) I’m sure both the civil engineering and tourism folks are working on spinning up alternative sites.

Grindavik, for what it’s worth, keeps bouncing between being evacuated and residents griping so much they get let back in. The Icelandic government has an offer on the table to purchase people’s homes in the town, so they move out. I think the plan is probably to abandon the town, since it’s possible this eruptive period could last hundreds of years. (Or not! We have no idea, really, just past data and informed guesses.)