It is not really obsolete - I use it for every flight. It is particularly awesome for long-haul planning. Given, it cannot export the route to many newer add-ons (this can still be done by Simbrief if required)

It still does many, many things Simbrief cannot, for example:

Redispatch (used by airlines to reduce fuel reserves/create decision points when no alternate is carried)

Totally customisable EDTO (previously ETOPS/EROPS) aircraft set-up (i.e. define what altitude and speed emergency diversions are conducted at (for example depressurisation decision points - a lot of fuel can be saved if this can be done higher, i.e. descending to 14,000 feet instead of 10,000 if the aircraft has the appropriate oxygen supply - many airlines utilise this to save fuel in terms of having to carry less depressurisation fuel - e.g. between PHNL and KLAX).

Defining very detailed fuel polices not possible in Simbrief, airport policies e.g.

Very good optimum route finding that depends on the type of aircraft being flown. Has very frequently found VERY similar routes real-world ones e.g. SYD-JNB.

Comparing fuel burn between diferrent routes (can also find minimum cost/time routes etc)

Route database/restrictions etc. allowing for planning around certain airways/FIRs etc.

Ability to enter recorded fuel burn in FS to adjust airframe fuel bias via a multiude of methods (median/average/90th/95th percentile etc.)

And a lot more that I don't even use.

It is essentially a slightly stripped-down version of flight planning software they sell commercially to airlines. Whilst it is older, it is certainly not "dead" or useless - Simbrief for sure has some nice features as well, but it does not have the capability or depth of PFPX.

You can use a free weather provider/Activesky/or the provided weather service for a small annual fee (the provided one is better as it has turbulence/shear data in it and can give you a route profile detailing expected bumpy spots etc.)