I think it's perfectly normal to expect someone to give up their old citizenship when becoming citizen in a different country. When you become a citizen, that country is responsible for getting you out of international conflicts and arranging passports (which are essentially documents that say "you should let this person in because of the good relationship our two governments have"), and in turn you're expected to turn up for the draft and decide in national policy.

There are certainly countries where gaining citizenship is a challenge, but the Dutch terms for EU migrants the minimum requirements ("speaking the language somewhat fluently, having lived there legally for five years, filling out paperwork") aren't that difficult. Getting through the process takes effort, for sure, but it's not the challenge most people in the world will face (the "living in the country legally for five years" part, mostly; without student visas or special deals between your old government and the Dutch government, you're not likely to get a work visa as any random person on earth).