Hi, LFC fan here, before you all roll eyes and jump on, actually wanted to put some positive notes on the conversation/worries you have above (CL qualie/development as a team/going backwards)
Speaking from relatively recent experience...
Firstly buying 'names' isn't the be all and end all. I don't mean this to be patronising, and been there many times over the last decade or so, when i've been the same and you're worried you're going to get trumped for x, y or z. Actually whats much more important is having a good scouting team, an identity on the pitch which is attractive to players, and some patience to build.
Robertson is the prime example, most LFC fans were pretty underwhelmed, let alone oppo fans, but our scouting team and 'sporting department' had clearly done their homework, clearly seen he had the energy and skills to fit into a style of play, and room to improve as well. squad/first team improved..
Then waiting for the right players, when discussing VVD the conversation always seems to centre on his cost, he was always going to be good etc, but what impressed me about my club on that, was having identified him (and then ballsed up in approaches in the summer), we waited, we didn't let the money burn a hole in the pocket, and make rash decisions, Klopp just thought balls to it, we'll just have to carry on with Keegan-ball trying to score more than the oppo for another few months and we'll go and get our man in the next window.
I see parrallels with your striker options, it's ballsy, don't get me wrong, and maybe not the same situation, but feels like it from the outside, why burn a big pile of cash on a short term 'name' on loan or even worse a 2 year contract, when it could be damaging to the dressing room, could use up much needed wageroll for the actual target you want etc..
Anyways.. TL:DR by now I expect, but out of all the teams in 'transition' at the moment, I think you're in the best shape, whether you get 4th or not, and city aside, as they'll just splash cash anyway, but Frank is driving a real identity of play on the pitch, your young lads, who'll be the lynch-pins of your team in 21/22/23 etc are getting invaluable game time and experience (parallels here with TAA), and just buying ready made players isn't, I think, where you as a club need to be now, it'll take a season or two longer, but with the youngsters developing and young coach building something, you have the chance to build something special rather than a quick flash in the pan season.
just my thoughts anyway..