Just my two cents: I mean in generally she’s not wrong, some things with Interrail could definitely be improved and made easier. BUT everyone who invests 5 minutes of thinking before buying an Interrail Pass knows that France & Spain are the WORST countries for using Interrails.
Actually France is still quite ok because you can get anywhere without using a reservation. Spain is a bit stupid. 

The information about limits of interrail reservations is also not really true. There was but now there is just a higher price if the contingent is not available anymore AFAIK. And not Interrail is guilty for this but the local railway companies and their ridiculous rules… 

13 in the dozen for that.

Again: it seems an un-avoidable feat of all newbee pass users to exactly just want to use the most difficult and hard to get trains and then complain that in hi-season these are full.

Though OTOH the former routes so populair-all the way to GR or TR have also been severely curtailed and the countries easy to travel in are in low demand for tourists

Countries easy to travel in are in low demand for tourists??? What? Lol.
So Switzerland, Germany, Austria, Netherlands, Belgium, UK are non-touristy destinations? 

I'm sorry to say this, but this above is typically a case of someone who write and blames on others without seeking-out how Interrail in some countries works and doesn't want to accept her own guilt in some cases). This does not change the fact that Spain might be avoided for interrail-trips, or you must know somebody there who can buy the reservations for you, (so if you van travel with regional-trains, buying-tickets would be more cheap than using a travel-day of a non-continious-pass). When I travel trough France, I plan these trips quite early, so I'm sure that I only have to pay € 12 extra for an Interrail-reservation. With some Nighttrain-reservations too. In Italy it could be cheaper to buy an Super-Economy with Single-sleeper (starting at € 76,90), instead of paying € 124 for the same sleeper-reservation. The fact that I can't change the travel-date, or give my Super-Economy back, it's for saving € 47,10 really worth!

Some Interrail-unfriendly countries might be:
Spain, (absolutely),
France (often, if you don't like to plan your trip, avoid crossing the border with TGV), Italy (sometimes, especially by crossing the border with EC, IC, of High-speed-trains),
Sweden, (if you travel with 1. Class Pass and often use a X2000/X3000, where a reservation in compulsory: it might be better to reserve a seat in 2. Class Calm, instead of 1. Class: it's 60-65% cheaper, seats are just few worse than in 1. class and apart from no free coffee/tea, there's no romour of mobile-phoning people).

I  agree! By the way: the same friend in Berlin who sent me the article made all our AVE reservations for last summer (yes, in Germany this really works!), and thanks to him we were able to make our round trip all around Spain and Portugal without a single problem…

Having traveled by train in most Interrail countries myself however, it’s hard to understand why Spain still combines such a next-century railway network with such a last-century reservation system… But that’s just my two pence

That's passenger-hostile RENFE for you. The trains are fine but all the rest..