That's a fair criticism, and i guess a natural solution would be to tighten how it operates, as well as add limitations to embarkation distance, maybe requiring to hop across multiple fortresses to get to a destination very far far away with this method. If you can successfully operate & grow a fortress using minimum or no materials then indeed the game might already be too easy for you
The starting experience will be the hardest based on how and where you embark and subsequently pushing foward into more dangerous areas after settling on a safe grassland or mountain biome with no local threats in order to build up your 'starter' fortress going from there. Unless the previous fortress is destroyed there would be a guranteed trade/migration link, but risk of isolating yourself at the end of the chain, and roads will likely spring up between you.
Another thing would be whether the journey's should be rendered in real time up until the point of arrival, and how the journeys are made via overland travel, cavern travel & use of sea & air and present dangers along the way. Compared with traditional retiring the fortress, embarking anywhere and arriving in a week you'd think the current method is impractically super-fast, if not for the fixed world rate of embark point budgeting.
- If you're both run by the same baron, it would be interesting if the fortress prior to you was more involved in defending and requesting aid & mandates from your fortress too, but it really depends on who is the direct junior partner (Monarch > Everybody in the direct fortress connection chain), and it would be cool if not frustrating to say the least if actions such as diplomats, petitions and trade agreements only occured in the baron's current holding (so effectively the traders visit you but you don't get any say on what has been ordered)
Subsequently choosing to have a more traditional independent method and instead assign either a mayor permanently OR a different baron instead of your previous fortress's current landholder will probably mean that said previous fortress won't interact with you so much rather than adjacency, so there will be no reinforcement troop relief or special interactions of that kind
Competition is good, it ironically makes more challenging gameplay and opportunities for worldgen things to happen such as loyalty cascade insurrections hurting/forging diplomatic links for better or worse.