The Venicci brand updates and changes its portfolio pretty regularly, so the discontinuation is not really unexpected. Just a portfolio update, I would call it. Now, they should have the Shadow 2.0 instead, and I believe many of their models can actually serve pretty similarly instead.
About the system, well, I must say I am not as much of a fan of Venicci, but that is, of course, very subjective. I feel like they're presenting themselves as a premium UK brand while their origin is Polish (their owner is actually the cheaper Bebetto brand). I simply know the quality requirements and manufacturing costs, and I don't think the price is worth it, BUT that, again, is a personal feeling. For those these a bit bulky, and a bit low-to-the-ground prams fit, they may offer a very nice value, especially when using the bassinet for the first 6 months, as it is quite comfy (I don't love the seat units much, they're too bulky and not so practical). All in all, prams better for the start, better for less tall parents, and good for bumpy roads, not for traveling by car often.
The Isofix base depends on the car seat you choose, and I definitely recommend NOT getting the color-matched one - rather, just order the adapters that accept Maxi-Cosi/Cybex/Joie car seats instead, and get an Isofix base to the car seat. There is no Isofix base matching a stroller, just a car seat.
The no-brand, OLDER car seats included with the 3in1 systems did not offer the Isofix base option - but, of course, one CAN live with just the seat belt car seat fastening. Not, the ULTRALITE and AeroFIX seats can be paired with the sold-separately IQ BASE from Venicci. I would still recommend a better brand car seat mentioned above, though.