Can still be fine for opensource/hobby work, anything professional needs better integration with the individual platform native UI apis.
Which is one of the reasons Electron became so popular — nobody has any expectations from a webapp UI, yet they still look better than Qt/GTK/wx on average...
So my opinion is if you want an app that looks perfect in screenshots or your customers are liking the buttonsand complain if the corners are not round enough then you should use the native looking stuff, but if your customers do their job using this app and every minute lost because of bugs. missing feature or bad UX then the look of the toolkit is not the issue, focus on what the customer is doing , see where you can improve his work and you will have happy customers.